diff --git a/mozilla/caps/src/nsBasePrincipal.cpp b/mozilla/caps/src/nsBasePrincipal.cpp
index 1c8fd220596..71e7b75c9cd 100644
--- a/mozilla/caps/src/nsBasePrincipal.cpp
+++ b/mozilla/caps/src/nsBasePrincipal.cpp
@@ -301,13 +301,13 @@ nsBasePrincipal::GetPreferences(char** aPrefName, char** aID,
         capList->granted = &grantedListStr;
         capList->denied = &deniedListStr;        
         mCapabilities->Enumerate(AppendCapability, (void*)capList);
-        if (grantedListStr.Length() > 0)
+        if (!grantedListStr.IsEmpty())
         {
             grantedListStr.Truncate(grantedListStr.Length()-1);
             *aGrantedList = ToNewCString(grantedListStr);
             if (!*aGrantedList) return NS_ERROR_OUT_OF_MEMORY;
         }
-        if (deniedListStr.Length() > 0)
+        if (!deniedListStr.IsEmpty())
         {
             deniedListStr.Truncate(deniedListStr.Length()-1);
             *aDeniedList = ToNewCString(deniedListStr);
diff --git a/mozilla/chrome/src/nsChromeRegistry.cpp b/mozilla/chrome/src/nsChromeRegistry.cpp
index da716564b6d..1f1a8cfceea 100644
--- a/mozilla/chrome/src/nsChromeRegistry.cpp
+++ b/mozilla/chrome/src/nsChromeRegistry.cpp
@@ -484,7 +484,7 @@ SplitURL(nsIURI *aChromeURI, nsCString& aPackage, nsCString& aProvider, nsCStrin
   aProvider.Right(aFile, aProvider.Length() - (idx + 1));
   aProvider.Truncate(idx);
 
-  PRBool nofile = (aFile.Length() == 0);
+  PRBool nofile = aFile.IsEmpty();
   if (nofile) {
     // If there is no file, then construct the default file
     aFile = aPackage;
diff --git a/mozilla/content/base/src/nsScriptLoader.cpp b/mozilla/content/base/src/nsScriptLoader.cpp
index 6600910dc06..916c1fad3c6 100644
--- a/mozilla/content/base/src/nsScriptLoader.cpp
+++ b/mozilla/content/base/src/nsScriptLoader.cpp
@@ -705,7 +705,7 @@ DetectByteOrderMark(const unsigned char* aBytes, PRInt32 aLen, nsString& oCharse
     }
     break;
   }  // switch
-  return oCharset.Length() > 0;
+  return !oCharset.IsEmpty();
 }
 
 
diff --git a/mozilla/directory/xpcom/base/src/nsLDAPURL.cpp b/mozilla/directory/xpcom/base/src/nsLDAPURL.cpp
index e4ab32fbf32..9a0e2843e13 100644
--- a/mozilla/directory/xpcom/base/src/nsLDAPURL.cpp
+++ b/mozilla/directory/xpcom/base/src/nsLDAPURL.cpp
@@ -91,7 +91,7 @@ nsLDAPURL::GetSpec(nsACString &_retval)
     
     spec = ((mOptions & OPT_SECURE) ? kLDAPSSLScheme : kLDAPScheme);
     spec.Append("://");
-    if (mHost.Length() > 0) {
+    if (!mHost.IsEmpty()) {
         spec.Append(mHost);
     }
     if (mPort > 0) {
@@ -99,7 +99,7 @@ nsLDAPURL::GetSpec(nsACString &_retval)
         spec.AppendInt(mPort);
     }
     spec.Append('/');
-    if (mDN.Length() > 0) {
+    if (!mDN.IsEmpty()) {
         spec.Append(mDN);
     }
 
@@ -115,7 +115,7 @@ nsLDAPURL::GetSpec(nsACString &_retval)
         }
     }
 
-    if ((mScope) || mFilter.Length()) {
+    if (mScope || !mFilter.IsEmpty()) {
         spec.Append((count ? "?" : "??"));
         if (mScope) {
             if (mScope == SCOPE_ONELEVEL) {
@@ -124,7 +124,7 @@ nsLDAPURL::GetSpec(nsACString &_retval)
                 spec.Append("sub");
             }
         }
-        if (mFilter.Length()) {
+        if (!mFilter.IsEmpty()) {
             spec.Append('?');
             spec.Append(mFilter);
         }
diff --git a/mozilla/docshell/base/nsDefaultURIFixup.cpp b/mozilla/docshell/base/nsDefaultURIFixup.cpp
index e715941f123..bfba2d17558 100644
--- a/mozilla/docshell/base/nsDefaultURIFixup.cpp
+++ b/mozilla/docshell/base/nsDefaultURIFixup.cpp
@@ -314,7 +314,7 @@ PRBool nsDefaultURIFixup::MakeAlternateURI(nsIURI *aURI)
     // Security - URLs with user / password info should NOT be fixed up
     nsCAutoString userpass;
     aURI->GetUserPass(userpass);
-    if (userpass.Length() > 0) {
+    if (!userpass.IsEmpty()) {
         return PR_FALSE;
     }
 
@@ -364,12 +364,12 @@ PRBool nsDefaultURIFixup::MakeAlternateURI(nsIURI *aURI)
     }
     else if (numDots == 1)
     {
-        if (prefix.Length() > 0 &&
+        if (!prefix.IsEmpty() &&
                 oldHost.EqualsIgnoreCase(prefix.get(), prefix.Length())) {
             newHost.Assign(oldHost);
             newHost.Append(suffix);
         }
-        else if (suffix.Length() > 0) {
+        else if (!suffix.IsEmpty()) {
             newHost.Assign(prefix);
             newHost.Append(oldHost);
         }
diff --git a/mozilla/editor/libeditor/base/SetDocTitleTxn.cpp b/mozilla/editor/libeditor/base/SetDocTitleTxn.cpp
index 3c170894fb4..1db8b0eac23 100644
--- a/mozilla/editor/libeditor/base/SetDocTitleTxn.cpp
+++ b/mozilla/editor/libeditor/base/SetDocTitleTxn.cpp
@@ -192,7 +192,7 @@ nsresult SetDocTitleTxn::SetDomTitle(const nsAString& aTitle)
 
   // Append a text node under the TITLE
   //  only if the title text isn't empty
-  if (titleNode && aTitle.Length() > 0)
+  if (titleNode && !aTitle.IsEmpty())
   {
     nsCOMPtr<nsIDOMText> textNode;
     res = domDoc->CreateTextNode(aTitle, getter_AddRefs(textNode));
diff --git a/mozilla/editor/libeditor/html/nsHTMLCSSUtils.cpp b/mozilla/editor/libeditor/html/nsHTMLCSSUtils.cpp
index a642520859b..4a89c5e97ca 100644
--- a/mozilla/editor/libeditor/html/nsHTMLCSSUtils.cpp
+++ b/mozilla/editor/libeditor/html/nsHTMLCSSUtils.cpp
@@ -1069,8 +1069,8 @@ nsHTMLCSSUtils::HasClassOrID(nsIDOMElement * aElement, PRBool & aReturn)
 
   // we need to make sure that if the element has an id or a class attribute,
   // the attribute is not the empty string
-  aReturn = ((isClassSet && (0 != classVal.Length())) ||
-             (isIdSet    && (0 != idVal.Length())));
+  aReturn = ((isClassSet && !classVal.IsEmpty()) ||
+             (isIdSet    && !idVal.IsEmpty()));
   return NS_OK;
 }
 
diff --git a/mozilla/editor/libeditor/html/nsHTMLDataTransfer.cpp b/mozilla/editor/libeditor/html/nsHTMLDataTransfer.cpp
index c051c352cab..2f686fb0ba1 100644
--- a/mozilla/editor/libeditor/html/nsHTMLDataTransfer.cpp
+++ b/mozilla/editor/libeditor/html/nsHTMLDataTransfer.cpp
@@ -2073,7 +2073,7 @@ nsHTMLEditor::InsertAsCitedQuotation(const nsAString & aQuotedText,
         NS_NAMED_LITERAL_STRING(citestr, "cite");
         newElement->SetAttribute(NS_LITERAL_STRING("type"), citestr);
 
-        if (aCitation.Length() > 0)
+        if (!aCitation.IsEmpty())
           newElement->SetAttribute(citestr, aCitation);
 
         // Set the selection inside the blockquote so aQuotedText will go there:
diff --git a/mozilla/editor/libeditor/html/nsHTMLEditUtils.cpp b/mozilla/editor/libeditor/html/nsHTMLEditUtils.cpp
index ded7b69e454..deedff3da7e 100644
--- a/mozilla/editor/libeditor/html/nsHTMLEditUtils.cpp
+++ b/mozilla/editor/libeditor/html/nsHTMLEditUtils.cpp
@@ -296,7 +296,7 @@ nsHTMLEditUtils::IsLink(nsIDOMNode *aNode)
   if (anchor)
   {
     nsAutoString tmpText;
-    if (NS_SUCCEEDED(anchor->GetHref(tmpText)) && tmpText.get() && tmpText.Length() != 0)
+    if (NS_SUCCEEDED(anchor->GetHref(tmpText)) && !tmpText.IsEmpty())
       return PR_TRUE;
   }
   return PR_FALSE;
@@ -310,7 +310,7 @@ nsHTMLEditUtils::IsNamedAnchor(nsIDOMNode *aNode)
   if (anchor)
   {
     nsAutoString tmpText;
-    if (NS_SUCCEEDED(anchor->GetName(tmpText)) && tmpText.get() && tmpText.Length() != 0)
+    if (NS_SUCCEEDED(anchor->GetName(tmpText)) && !tmpText.IsEmpty())
       return PR_TRUE;
   }
   return PR_FALSE;
diff --git a/mozilla/editor/libeditor/html/nsHTMLEditor.cpp b/mozilla/editor/libeditor/html/nsHTMLEditor.cpp
index 10e8a314786..920718ac4d4 100644
--- a/mozilla/editor/libeditor/html/nsHTMLEditor.cpp
+++ b/mozilla/editor/libeditor/html/nsHTMLEditor.cpp
@@ -2602,7 +2602,7 @@ nsHTMLEditor::GetHTMLBackgroundColorState(PRBool *aMixed, nsAString &aOutColor)
     if (NS_FAILED(res)) return res;
 
     // Done if we have a color explicitly set
-    if (aOutColor.Length() > 0)
+    if (!aOutColor.IsEmpty())
       return NS_OK;
 
     // Once we hit the body, we're done
@@ -2995,7 +2995,7 @@ nsHTMLEditor::Align(const nsAString& aAlignType)
 NS_IMETHODIMP
 nsHTMLEditor::GetElementOrParentByTagName(const nsAString& aTagName, nsIDOMNode *aNode, nsIDOMElement** aReturn)
 {
-  if (aTagName.Length() == 0 || !aReturn )
+  if (aTagName.IsEmpty() || !aReturn )
     return NS_ERROR_NULL_POINTER;
   
   nsresult res = NS_OK;
@@ -3525,7 +3525,7 @@ nsHTMLEditor::SetHTMLBackgroundColor(const nsAString& aColor)
                                                  getter_AddRefs(element));
   if (NS_FAILED(res)) return res;
 
-  PRBool setColor = (aColor.Length() > 0);
+  PRBool setColor = !aColor.IsEmpty();
 
   NS_NAMED_LITERAL_STRING(bgcolor, "bgcolor");
   if (element)
@@ -4608,7 +4608,7 @@ void nsHTMLEditor::IsTextPropertySetByContent(nsIDOMNode        *aNode,
         {
           element->GetAttribute(*aAttribute, value);
           if (outValue) *outValue = value;
-          if (value.Length())
+          if (!value.IsEmpty())
           {
             if (!aValue) {
               found = PR_TRUE;
diff --git a/mozilla/editor/libeditor/html/nsHTMLEditorStyle.cpp b/mozilla/editor/libeditor/html/nsHTMLEditorStyle.cpp
index 8e647908a6b..bd7bdbabe94 100644
--- a/mozilla/editor/libeditor/html/nsHTMLEditorStyle.cpp
+++ b/mozilla/editor/libeditor/html/nsHTMLEditorStyle.cpp
@@ -1144,10 +1144,10 @@ NS_IMETHODIMP nsHTMLEditor::GetInlineProperty(nsIAtom *aProperty,
   if (!aProperty || !aFirst || !aAny || !aAll)
     return NS_ERROR_NULL_POINTER;
   const nsAString *att = nsnull;
-  if (aAttribute.Length())
+  if (!aAttribute.IsEmpty())
     att = &aAttribute;
   const nsAString *val = nsnull;
-  if (aValue.Length())
+  if (!aValue.IsEmpty())
     val = &aValue;
   return GetInlinePropertyBase( aProperty, att, val, aFirst, aAny, aAll, nsnull);
 }
@@ -1164,10 +1164,10 @@ NS_IMETHODIMP nsHTMLEditor::GetInlinePropertyWithAttrValue(nsIAtom *aProperty,
   if (!aProperty || !aFirst || !aAny || !aAll)
     return NS_ERROR_NULL_POINTER;
   const nsAString *att = nsnull;
-  if (aAttribute.Length())
+  if (!aAttribute.IsEmpty())
     att = &aAttribute;
   const nsAString *val = nsnull;
-  if (aValue.Length())
+  if (!aValue.IsEmpty())
     val = &aValue;
   return GetInlinePropertyBase( aProperty, att, val, aFirst, aAny, aAll, &outValue);
 }
@@ -1863,7 +1863,7 @@ nsHTMLEditor::HasStyleOrIdOrClass(nsIDOMElement * aElement, PRBool *aHasStyleOrI
   *aHasStyleOrIdOrClass = PR_TRUE;
   nsresult res = GetAttributeValue(aElement,  NS_LITERAL_STRING("style"), styleVal, &isStyleSet);
   if (NS_FAILED(res)) return res;
-  if (!isStyleSet || (0 == styleVal.Length())) {
+  if (!isStyleSet || styleVal.IsEmpty()) {
     res = mHTMLCSSUtils->HasClassOrID(aElement, *aHasStyleOrIdOrClass);
     if (NS_FAILED(res)) return res;
   }
diff --git a/mozilla/editor/libeditor/text/nsInternetCiter.cpp b/mozilla/editor/libeditor/text/nsInternetCiter.cpp
index b20fb8655e8..67fc41e56ac 100644
--- a/mozilla/editor/libeditor/text/nsInternetCiter.cpp
+++ b/mozilla/editor/libeditor/text/nsInternetCiter.cpp
@@ -273,7 +273,7 @@ nsInternetCiter::Rewrap(const nsAString& aInString,
 
     // Special case: if this is a blank line, maintain a blank line
     // (retain the original paragraph breaks)
-    if (tString[posInString] == nl && aOutString.Length() > 0)
+    if (tString[posInString] == nl && !aOutString.IsEmpty())
     {
       if (aOutString.Last() != nl)
         aOutString.Append(nl);
diff --git a/mozilla/editor/libeditor/text/nsPlaintextEditor.cpp b/mozilla/editor/libeditor/text/nsPlaintextEditor.cpp
index fb1b8b52edf..357a9bf9b42 100644
--- a/mozilla/editor/libeditor/text/nsPlaintextEditor.cpp
+++ b/mozilla/editor/libeditor/text/nsPlaintextEditor.cpp
@@ -319,7 +319,7 @@ nsPlaintextEditor::SetDocumentCharacterSet(const nsAString & characterSet)
               return NS_ERROR_FAILURE; 
 
             // Set attributes to the created element 
-            if (resultNode && characterSet.Length() > 0) { 
+            if (resultNode && !characterSet.IsEmpty()) { 
               metaElement = do_QueryInterface(resultNode); 
               if (metaElement) { 
                 // not undoable, undo should undo CreateNode 
@@ -1266,7 +1266,7 @@ nsPlaintextEditor::SetWrapWidth(PRInt32 aWrapColumn)
 
   // If we have other style left, trim off any existing semicolons
   // or whitespace, then add a known semicolon-space:
-  if (styleValue.Length() > 0)
+  if (!styleValue.IsEmpty())
   {
     styleValue.Trim("; \t", PR_FALSE, PR_TRUE);
     styleValue.Append(NS_LITERAL_STRING("; "));
@@ -1451,7 +1451,7 @@ nsPlaintextEditor::GetAndInitDocEncoder(const nsAString& aFormatType,
   rv = docEncoder->Init(doc, aFormatType, aFlags);
   NS_ENSURE_SUCCESS(rv, rv);
 
-  if (aCharset.Length() != 0
+  if (!aCharset.IsEmpty()
     && !(aCharset.Equals(NS_LITERAL_STRING("null"))))
     docEncoder->SetCharset(aCharset);
 
diff --git a/mozilla/embedding/browser/activex/src/control/MozillaBrowser.cpp b/mozilla/embedding/browser/activex/src/control/MozillaBrowser.cpp
index 68920723367..1b11a68c223 100644
--- a/mozilla/embedding/browser/activex/src/control/MozillaBrowser.cpp
+++ b/mozilla/embedding/browser/activex/src/control/MozillaBrowser.cpp
@@ -324,7 +324,7 @@ void CMozillaBrowser::ShowURIPropertyDlg(const nsAString &aURI, const nsAString
     CPPageDlg linkDlg;
     dlg.AddPage(&linkDlg);
 
-    if (aURI.Length() > 0)
+    if (!aURI.IsEmpty())
     {
         linkDlg.mType = aContentType;
         linkDlg.mURL = aURI;
@@ -844,7 +844,7 @@ LRESULT CMozillaBrowser::OnLinkOpen(WORD wNotifyCode, WORD wID, HWND hWndCtl, BO
         anchorElement->GetHref(uri);
     }
 
-    if (uri.Length() > 0)
+    if (!uri.IsEmpty())
     {
         CComBSTR bstrURI(uri.get());
         CComVariant vFlags(0);
@@ -865,7 +865,7 @@ LRESULT CMozillaBrowser::OnLinkOpenInNewWindow(WORD wNotifyCode, WORD wID, HWND
         anchorElement->GetHref(uri);
     }
 
-    if (uri.Length() > 0)
+    if (!uri.IsEmpty())
     {
         CComBSTR bstrURI(uri.get());
         CComVariant vFlags(navOpenInNewWindow);
@@ -886,7 +886,7 @@ LRESULT CMozillaBrowser::OnLinkCopyShortcut(WORD wNotifyCode, WORD wID, HWND hWn
         anchorElement->GetHref(uri);
     }
 
-    if (uri.Length() > 0 && OpenClipboard())
+    if (!uri.IsEmpty() && OpenClipboard())
     {
         EmptyClipboard();
 
diff --git a/mozilla/embedding/components/webbrowserpersist/src/nsWebBrowserPersist.cpp b/mozilla/embedding/components/webbrowserpersist/src/nsWebBrowserPersist.cpp
index bc598c4f831..78eaf0004e1 100644
--- a/mozilla/embedding/components/webbrowserpersist/src/nsWebBrowserPersist.cpp
+++ b/mozilla/embedding/components/webbrowserpersist/src/nsWebBrowserPersist.cpp
@@ -1327,7 +1327,7 @@ nsWebBrowserPersist::GetDocEncoderContentType(nsIDOMDocument *aDocument, const P
         if (nsDoc)
         {
             nsAutoString type;
-            if (NS_SUCCEEDED(nsDoc->GetContentType(type)) && type.Length() > 0)
+            if (NS_SUCCEEDED(nsDoc->GetContentType(type)) && !type.IsEmpty())
             {
                 contentType.Assign(type);
             }
@@ -1344,7 +1344,7 @@ nsWebBrowserPersist::GetDocEncoderContentType(nsIDOMDocument *aDocument, const P
     //   text/html
     //   text/plain
 
-    if (contentType.Length() > 0 &&
+    if (!contentType.IsEmpty() &&
         !contentType.Equals(defaultContentType, nsCaseInsensitiveStringComparator()))
     {
         // Check if there is an encoder for the desired content type
@@ -1542,7 +1542,7 @@ nsresult nsWebBrowserPersist::SaveDocumentInternal(
         // Get the content type to save with
         nsXPIDLString realContentType;
         GetDocEncoderContentType(aDocument,
-            (mContentType.Length() > 0) ? mContentType.get() : nsnull,
+            !mContentType.IsEmpty() ? mContentType.get() : nsnull,
             getter_Copies(realContentType));
 
         nsCAutoString contentType; contentType.AssignWithConversion(realContentType);
@@ -1599,7 +1599,7 @@ nsresult nsWebBrowserPersist::SaveDocuments()
         // Get the content type
         nsXPIDLString realContentType;
         GetDocEncoderContentType(docData->mDocument,
-            (mContentType.Length() > 0) ? mContentType.get() : nsnull,
+            !mContentType.IsEmpty() ? mContentType.get() : nsnull,
             getter_Copies(realContentType));
 
         nsCAutoString contentType; contentType.AssignWithConversion(realContentType.get());
@@ -1903,7 +1903,7 @@ nsWebBrowserPersist::CalculateAndAppendFileExt(nsIURI *aURI, nsIChannel *aChanne
     aChannel->GetContentType(contentType);
 
     // Get the content type from the MIME service
-    if (contentType.Length() == 0)
+    if (contentType.IsEmpty())
     {
         nsCOMPtr<nsIURI> uri;
         aChannel->GetOriginalURI(getter_AddRefs(uri));
@@ -1914,7 +1914,7 @@ nsWebBrowserPersist::CalculateAndAppendFileExt(nsIURI *aURI, nsIChannel *aChanne
     }
 
     // Append the extension onto the file
-    if (contentType.Length())
+    if (!contentType.IsEmpty())
     {
         nsCOMPtr<nsIMIMEInfo> mimeInfo;
         mMIMEService->GetFromMIMEType(
@@ -3206,7 +3206,7 @@ nsWebBrowserPersist::SaveDocumentWithFixup(
         encoder->SetWrapColumn(mWrapColumn);
 
     nsAutoString charsetStr(aSaveCharset);
-    if (charsetStr.Length() == 0)
+    if (charsetStr.IsEmpty())
     {
         rv = aDocument->GetDocumentCharacterSet(charsetStr);
         if(NS_FAILED(rv))
diff --git a/mozilla/embedding/components/windowwatcher/src/nsWindowWatcher.cpp b/mozilla/embedding/components/windowwatcher/src/nsWindowWatcher.cpp
index d735c4eb01e..c4a69293638 100644
--- a/mozilla/embedding/components/windowwatcher/src/nsWindowWatcher.cpp
+++ b/mozilla/embedding/components/windowwatcher/src/nsWindowWatcher.cpp
@@ -1403,7 +1403,7 @@ nsWindowWatcher::FindItemWithName(
   *aFoundItem = 0;
 
   /* special cases */
-  if(name.Length() == 0)
+  if(name.IsEmpty())
     return NS_OK;
   if(name.EqualsIgnoreCase("_blank") || name.EqualsIgnoreCase("_new"))
     return NS_OK;
diff --git a/mozilla/embedding/lite/nsEmbedChromeRegistry.cpp b/mozilla/embedding/lite/nsEmbedChromeRegistry.cpp
index 8f2475446ef..325302a1989 100644
--- a/mozilla/embedding/lite/nsEmbedChromeRegistry.cpp
+++ b/mozilla/embedding/lite/nsEmbedChromeRegistry.cpp
@@ -107,7 +107,7 @@ SplitURL(nsIURI *aChromeURI, nsCString& aPackage, nsCString& aProvider, nsCStrin
   aProvider.Right(aFile, aProvider.Length() - (idx + 1));
   aProvider.Truncate(idx);
 
-  PRBool nofile = (aFile.Length() == 0);
+  PRBool nofile = aFile.IsEmpty();
   if (nofile) {
     // If there is no file, then construct the default file
     aFile = aPackage;
diff --git a/mozilla/extensions/sql/base/src/mozSqlResult.cpp b/mozilla/extensions/sql/base/src/mozSqlResult.cpp
index 7e46612bec7..c3c4bc51715 100644
--- a/mozilla/extensions/sql/base/src/mozSqlResult.cpp
+++ b/mozilla/extensions/sql/base/src/mozSqlResult.cpp
@@ -657,7 +657,7 @@ mozSqlResult::ClearRows()
 nsresult
 mozSqlResult::EnsureTableName()
 {
-  if (mTableName.Length() > 0)
+  if (!mTableName.IsEmpty())
     return NS_OK;
 
   nsAString::const_iterator start, end;
diff --git a/mozilla/extensions/sql/pgsql/src/mozSqlConnectionPgsql.cpp b/mozilla/extensions/sql/pgsql/src/mozSqlConnectionPgsql.cpp
index 7474c07cefc..052db7c5d9d 100644
--- a/mozilla/extensions/sql/pgsql/src/mozSqlConnectionPgsql.cpp
+++ b/mozilla/extensions/sql/pgsql/src/mozSqlConnectionPgsql.cpp
@@ -55,7 +55,7 @@ mozSqlConnectionPgsql::GetPrimaryKeys(const nsAString& aSchema, const nsAString&
     select = NS_LITERAL_STRING("SELECT n.nspname AS TABLE_SCHEM, ");
     from = NS_LITERAL_STRING(" FROM pg_catalog.pg_namespace n, pg_catalog.pg_class ct, pg_catalog.pg_class ci, pg_catalog.pg_attribute a, pg_catalog.pg_index i");
     where = NS_LITERAL_STRING(" AND ct.relnamespace = n.oid ");
-    if (aSchema.Length() > 0) {
+    if (!aSchema.IsEmpty()) {
       where.Append(NS_LITERAL_STRING(" AND n.nspname = '") + aSchema);
       where.Append(PRUnichar('\''));
     }
@@ -65,7 +65,7 @@ mozSqlConnectionPgsql::GetPrimaryKeys(const nsAString& aSchema, const nsAString&
     from = NS_LITERAL_STRING(" FROM pg_class ct, pg_class ci, pg_attribute a, pg_index i ");
   }
 
-  if (aTable.Length() > 0) {
+  if (!aTable.IsEmpty()) {
     where.Append(NS_LITERAL_STRING(" AND ct.relname = '") + aTable);
     where.Append(PRUnichar('\''));
   }
diff --git a/mozilla/extensions/wallet/src/nsBasicStreamGenerator.cpp b/mozilla/extensions/wallet/src/nsBasicStreamGenerator.cpp
index b5a16ae5807..f855d44f81f 100644
--- a/mozilla/extensions/wallet/src/nsBasicStreamGenerator.cpp
+++ b/mozilla/extensions/wallet/src/nsBasicStreamGenerator.cpp
@@ -82,7 +82,7 @@ NS_IMETHODIMP nsBasicStreamGenerator::GetLevel(float *aLevel) {
 NS_IMETHODIMP nsBasicStreamGenerator::GetByte(PRUint32 offset, PRUint8 *retval) {
   NS_ENSURE_ARG_POINTER(retval);
   nsresult rv = NS_OK;
-  if (mPassword.Length() == 0) {
+  if (mPassword.IsEmpty()) {
     /* this is the first time, so we need to get the password */
     nsCOMPtr<nsIPasswordSink> weakPasswordSink = do_QueryReferent(mWeakPasswordSink);
     if (!weakPasswordSink) {
diff --git a/mozilla/extensions/wallet/src/singsign.cpp b/mozilla/extensions/wallet/src/singsign.cpp
index 17c03f974d2..a55d7257133 100644
--- a/mozilla/extensions/wallet/src/singsign.cpp
+++ b/mozilla/extensions/wallet/src/singsign.cpp
@@ -1612,7 +1612,7 @@ si_PutData(const char *passwordRealm, nsVoidArray *signonData, PRBool save) {
   PRInt32 count = signonData->Count();
   for (PRInt32 i=0; i<count; i++) {
     data2 = NS_STATIC_CAST(si_SignonDataStruct*, signonData->ElementAt(i));
-    if (data2->isPassword && data2->value.Length()==0) {
+    if (data2->isPassword && data2->value.IsEmpty()) {
       return;
     }
   }
@@ -2339,8 +2339,8 @@ si_RememberSignonData
     data0 = NS_STATIC_CAST(si_SignonDataStruct*, signonData->ElementAt(pswd[0]));
     data1 = NS_STATIC_CAST(si_SignonDataStruct*, signonData->ElementAt(pswd[1]));
     data2 = NS_STATIC_CAST(si_SignonDataStruct*, signonData->ElementAt(pswd[2]));
-    if (data0->value.Length() == 0 || data1->value.Length() == 0 ||
-        data2->value.Length() == 0 || data1->value != data2->value) {
+    if (data0->value.IsEmpty() || data1->value.IsEmpty() ||
+        data2->value.IsEmpty() || data1->value != data2->value) {
       return;
     }
 
@@ -2450,7 +2450,7 @@ si_RestoreSignonData(nsIPrompt* dialog,
       LOG(("  got [name=%s value=%s]\n",
               NS_LossyConvertUCS2toASCII(data->name).get(),
               NS_LossyConvertUCS2toASCII(data->value).get()));
-      if(correctedName.Length() && (data->name == correctedName)) {
+      if(!correctedName.IsEmpty() && (data->name == correctedName)) {
         nameFound = PR_TRUE;
       }
     }
@@ -2473,7 +2473,7 @@ si_RestoreSignonData(nsIPrompt* dialog,
   if (user) {
     data = NS_STATIC_CAST(si_SignonDataStruct *,
                     user->signonData_list.ElementAt(0)); /* 1st item on form */
-    if(data->isPassword && correctedName.Length() && (data->name == correctedName)) {
+    if(data->isPassword && !correctedName.IsEmpty() && (data->name == correctedName)) {
       /* current item is first item on form and is a password */
       user = (passwordRealm, MK_SIGNON_PASSWORDS_FETCH);
       if (user) {
@@ -2505,7 +2505,7 @@ si_RestoreSignonData(nsIPrompt* dialog,
       LOG(("  got [name=%s value=%s]\n",
               NS_LossyConvertUCS2toASCII(data->name).get(),
               NS_LossyConvertUCS2toASCII(data->value).get()));
-      if(correctedName.Length() && (data->name == correctedName)) {
+      if(!correctedName.IsEmpty() && (data->name == correctedName)) {
         nsAutoString password;
         if (NS_SUCCEEDED(si_Decrypt(data->value, password))) {
           *value = ToNewUnicode(password);
@@ -2581,7 +2581,7 @@ si_RestoreOldSignonDataFromBrowser
 
   /* get the data from previous time this URL was visited */
   si_lock_signon_list();
-  if (username.Length() != 0) {
+  if (!username.IsEmpty()) {
     user = si_GetSpecificUser(passwordRealm, username, NS_ConvertASCIItoUCS2(USERNAMEFIELD));
   } else {
     si_LastFormForWhichUserHasBeenSelected = -1;
@@ -2776,17 +2776,17 @@ SINGSIGN_PromptPassword
   }
 
   /* get previous password used with this username, pick first user if no username found */
-  si_RestoreOldSignonDataFromBrowser(dialog, passwordRealm, (username.Length() == 0), username, password);
+  si_RestoreOldSignonDataFromBrowser(dialog, passwordRealm, username.IsEmpty(), username, password);
+
+  *pwd = ToNewUnicode(password);
 
   /* return if a password was found */
-  if (password.Length() != 0) {
-    *pwd = ToNewUnicode(password);
+  if (!password.IsEmpty()) {
     *pressedOK = PR_TRUE;
     return NS_OK;
   }
 
   /* no password found, get new password from user */
-  *pwd = ToNewUnicode(password);
   PRBool checked = PR_FALSE;
   res = si_CheckGetPassword(pwd, dialogTitle, text, dialog, savePassword, &checked);
   if (NS_FAILED(res)) {
@@ -2832,7 +2832,7 @@ SINGSIGN_Prompt
   si_RestoreOldSignonDataFromBrowser(dialog, passwordRealm, PR_TRUE, emptyUsername, data);
 
   /* return if data was found */
-  if (data.Length() != 0) {
+  if (!data.IsEmpty()) {
     *resultText = ToNewUnicode(data);
     *pressedOK = PR_TRUE;
     return NS_OK;
@@ -2968,9 +2968,9 @@ SINGSIGN_HaveData(nsIPrompt* dialog, const char *passwordRealm, const PRUnichar
   }
 
   /* get previous data used with this username, pick first user if no username found */
-  si_RestoreOldSignonDataFromBrowser(dialog, passwordRealm, (usernameForLookup.Length() == 0), usernameForLookup, data);
+  si_RestoreOldSignonDataFromBrowser(dialog, passwordRealm, usernameForLookup.IsEmpty(), usernameForLookup, data);
 
-  if (data.Length()) {
+  if (!data.IsEmpty()) {
     *retval = PR_TRUE;
   }
 
diff --git a/mozilla/extensions/wallet/src/wallet.cpp b/mozilla/extensions/wallet/src/wallet.cpp
index b4fef8d8d85..1d79a914f79 100644
--- a/mozilla/extensions/wallet/src/wallet.cpp
+++ b/mozilla/extensions/wallet/src/wallet.cpp
@@ -2330,14 +2330,14 @@ wallet_GetSchemaFromDisplayableText
     text = temp;
 
     /* done if we've obtained enough text from which to determine the schema */
-    if (text.Length()) {
+    if (!text.IsEmpty()) {
       someTextFound = PR_TRUE;
 
       TextToSchema(text, schema);
       if (!schema.IsEmpty()) {
 
         /* schema found, process positional schema if any */
-        if (!schema.IsEmpty() && schema.First() == '%') {
+        if (schema.First() == '%') {
           wallet_ResolvePositionalSchema(elementNode, schema);
         }
 
@@ -2892,7 +2892,7 @@ PRIVATE PRBool
 wallet_Capture(nsIDocument* doc, const nsString& field, const nsString& value, nsACString& schema)
 {
   /* do nothing if there is no value */
-  if (!value.Length()) {
+  if (value.IsEmpty()) {
     return PR_FALSE;
   }
 
@@ -3673,7 +3673,7 @@ wallet_CaptureInputElement(nsIDOMNode* elementNode, nsIDocument* doc) {
           }
           if (schema.IsEmpty()) {
             /* get schema from displayable text if possible */
-            wallet_GetSchemaFromDisplayableText(inputElement, schema, (value.Length()==0));
+            wallet_GetSchemaFromDisplayableText(inputElement, schema, value.IsEmpty());
           }
           if (wallet_Capture(doc, field, value, schema)) {
             captured = PR_TRUE;
@@ -4034,7 +4034,7 @@ WLLT_OnSubmit(nsIContent* currentForm, nsIDOMWindowInternal* window) {
                       if (NS_SUCCEEDED(rv)) {
                         data = new si_SignonDataStruct;
                         data->value = value;
-                        if (field.Length() && field.CharAt(0) == '\\') {
+                        if (!field.IsEmpty() && field.CharAt(0) == '\\') {
                           /*
                            * Note that data saved for browser-generated logins (e.g. http
                            * authentication) use artificial field names starting with
@@ -4084,7 +4084,7 @@ WLLT_OnSubmit(nsIContent* currentForm, nsIDOMWindowInternal* window) {
                             for (PRInt32 i=0; i<count; i++) {
                               mapElementPtr = NS_STATIC_CAST
                                 (wallet_MapElement*, wallet_DistinguishedSchema_list->ElementAt(i));
-                                  if (schema.Equals(mapElementPtr->item1, nsCaseInsensitiveCStringComparator()) && value.Length() > 0) {
+                                  if (schema.Equals(mapElementPtr->item1, nsCaseInsensitiveCStringComparator()) && !value.IsEmpty()) {
                                 hits++;
                                 if (hits > 1 && newValueFound) {
                                   OKToPrompt = PR_TRUE;
diff --git a/mozilla/extensions/webservices/schema/src/nsSchemaLoader.cpp b/mozilla/extensions/webservices/schema/src/nsSchemaLoader.cpp
index 21d96d197eb..181a25c49fa 100644
--- a/mozilla/extensions/webservices/schema/src/nsSchemaLoader.cpp
+++ b/mozilla/extensions/webservices/schema/src/nsSchemaLoader.cpp
@@ -1101,7 +1101,7 @@ nsSchemaLoader::GetNewOrUsedType(nsSchema* aSchema,
   // namespace associated with the prefix
   rv = ParseQualifiedName(aContext, aTypeName, prefix, 
                           localName, namespaceURI);
-  if ((prefix.Length() > 0) && NS_FAILED(rv)) {
+  if (!prefix.IsEmpty() && NS_FAILED(rv)) {
     // Unknown prefix
     return NS_ERROR_SCHEMA_UNKNOWN_PREFIX;
   }
@@ -1148,7 +1148,7 @@ nsSchemaLoader::ProcessElement(nsSchema* aSchema,
   // See if it's a reference or an actual element declaration
   nsAutoString ref;
   aElement->GetAttribute(NS_LITERAL_STRING("ref"), ref);
-  if (ref.Length() > 0) {
+  if (!ref.IsEmpty()) {
     nsSchemaElementRef* elementRef;
     
     elementRef = new nsSchemaElementRef(aSchema, ref);
@@ -1672,7 +1672,7 @@ nsSchemaLoader::ProcessSimpleContent(nsSchema* aSchema,
     if ((tagName == nsSchemaAtoms::sRestriction_atom) ||
         (tagName == nsSchemaAtoms::sExtension_atom)) {
       childElement->GetAttribute(NS_LITERAL_STRING("base"), baseStr);
-      if (baseStr.Length() == 0) {
+      if (baseStr.IsEmpty()) {
         return NS_ERROR_SCHEMA_MISSING_TYPE;
       }
       
@@ -1931,7 +1931,7 @@ nsSchemaLoader::ProcessComplexContent(nsSchema* aSchema,
     if ((tagName == nsSchemaAtoms::sRestriction_atom) ||
         (tagName == nsSchemaAtoms::sExtension_atom)) {
       childElement->GetAttribute(NS_LITERAL_STRING("base"), baseStr);
-      if (baseStr.Length() == 0) {
+      if (baseStr.IsEmpty()) {
         return NS_ERROR_SCHEMA_MISSING_TYPE;
       }
       
@@ -2118,7 +2118,7 @@ nsSchemaLoader::ProcessSimpleTypeRestriction(nsSchema* aSchema,
   nsCOMPtr<nsISchemaType> baseType;
   nsAutoString baseStr;
   aElement->GetAttribute(NS_LITERAL_STRING("base"), baseStr);
-  if (baseStr.Length() > 0) {
+  if (!baseStr.IsEmpty()) {
     rv = GetNewOrUsedType(aSchema, aElement, baseStr, 
                           getter_AddRefs(baseType));
     if (NS_FAILED(rv)) {
@@ -2211,7 +2211,7 @@ nsSchemaLoader::ProcessSimpleTypeList(nsSchema* aSchema,
   aElement->GetAttribute(NS_LITERAL_STRING("itemType"), itemTypeStr);
 
   nsCOMPtr<nsISchemaSimpleType> itemType;
-  if (itemTypeStr.Length() > 0) {
+  if (!itemTypeStr.IsEmpty()) {
     nsCOMPtr<nsISchemaType> type;
     rv = GetNewOrUsedType(aSchema, aElement, itemTypeStr, 
                           getter_AddRefs(type));
@@ -2273,7 +2273,7 @@ nsSchemaLoader::ProcessSimpleTypeUnion(nsSchema* aSchema,
   nsCOMPtr<nsISchemaSimpleType> memberType;
   nsAutoString memberTypes;
   aElement->GetAttribute(NS_LITERAL_STRING("memberTypes"), memberTypes);
-  if (memberTypes.Length() > 0) {
+  if (!memberTypes.IsEmpty()) {
     nsReadingIterator<PRUnichar> begin, end, tokenEnd;
 
     memberTypes.BeginReading(tokenEnd);
@@ -2356,7 +2356,7 @@ nsSchemaLoader::ProcessModelGroup(nsSchema* aSchema,
   aElement->GetAttribute(NS_LITERAL_STRING("ref"), ref);
   
   if ((aTagName == nsSchemaAtoms::sModelGroup_atom) &&
-      (ref.Length() > 0)) {
+      !ref.IsEmpty()) {
     nsSchemaModelGroupRef* modelGroupRef = new nsSchemaModelGroupRef(aSchema, 
                                                                      ref);
     if (!modelGroupRef) {
@@ -2583,7 +2583,7 @@ nsSchemaLoader::ProcessAttribute(nsSchema* aSchema,
 
   nsAutoString ref;
   aElement->GetAttribute(NS_LITERAL_STRING("ref"), ref);
-  if (ref.Length() > 0) {
+  if (!ref.IsEmpty()) {
     nsSchemaAttributeRef* attributeRef = new nsSchemaAttributeRef(aSchema,
                                                                   ref);
     if (!attributeRef) {
@@ -2633,7 +2633,7 @@ nsSchemaLoader::ProcessAttribute(nsSchema* aSchema,
       nsAutoString typeStr;
       aElement->GetAttribute(NS_LITERAL_STRING("type"), typeStr);
 
-      if (typeStr.Length() > 0) {
+      if (!typeStr.IsEmpty()) {
         nsCOMPtr<nsISchemaType> schemaType;
         rv = GetNewOrUsedType(aSchema, aElement, typeStr, 
                               getter_AddRefs(schemaType));
@@ -2669,7 +2669,7 @@ nsSchemaLoader::ProcessAttributeGroup(nsSchema* aSchema,
   nsAutoString ref;
   aElement->GetAttribute(NS_LITERAL_STRING("ref"), ref);
 
-  if (ref.Length() > 0) {
+  if (!ref.IsEmpty()) {
     nsSchemaAttributeGroupRef* attrRef = new nsSchemaAttributeGroupRef(aSchema,
                                                                        ref);
     if (!attrRef) {
@@ -2782,7 +2782,7 @@ nsSchemaLoader::ProcessFacet(nsSchema* aSchema,
 
   nsAutoString valueStr;
   aElement->GetAttribute(NS_LITERAL_STRING("value"), valueStr);
-  if (valueStr.Length() == 0) {
+  if (valueStr.IsEmpty()) {
     return NS_ERROR_SCHEMA_FACET_VALUE_ERROR;
   }
 
@@ -2879,14 +2879,14 @@ nsSchemaLoader::GetMinAndMax(nsIDOMElement* aElement,
   aElement->GetAttribute(NS_LITERAL_STRING("maxOccurs"), maxStr);
   
   PRInt32 rv;
-  if (minStr.Length() > 0) {
+  if (!minStr.IsEmpty()) {
     PRInt32 minVal = minStr.ToInteger(&rv);
     if (NS_SUCCEEDED(rv) && (minVal >= 0)) {
       *aMinOccurs = (PRUint32)minVal;
     }
   }
 
-  if (maxStr.Length() > 0) {
+  if (!maxStr.IsEmpty()) {
     if (maxStr.Equals(NS_LITERAL_STRING("unbounded"))) {
       *aMaxOccurs = nsISchemaParticle::OCCURRENCE_UNBOUNDED;
     }
diff --git a/mozilla/extensions/webservices/soap/src/nsSOAPCall.cpp b/mozilla/extensions/webservices/soap/src/nsSOAPCall.cpp
index 1987c730d1f..a4f64be20ba 100644
--- a/mozilla/extensions/webservices/soap/src/nsSOAPCall.cpp
+++ b/mozilla/extensions/webservices/soap/src/nsSOAPCall.cpp
@@ -130,7 +130,7 @@ NS_IMETHODIMP nsSOAPCall::Invoke(nsISOAPResponse ** _retval)
   nsresult rv;
   nsCOMPtr < nsISOAPTransport > transport;
 
-  if (mTransportURI.Length() == 0) {
+  if (mTransportURI.IsEmpty()) {
     return SOAP_EXCEPTION(NS_ERROR_NOT_INITIALIZED,"SOAP_TRANSPORT_URI", "No transport URI was specified.");
   }
 
@@ -172,7 +172,7 @@ NS_IMETHODIMP
   nsresult rv;
   nsCOMPtr < nsISOAPTransport > transport;
 
-  if (mTransportURI.Length() == 0) {
+  if (mTransportURI.IsEmpty()) {
     return SOAP_EXCEPTION(NS_ERROR_NOT_INITIALIZED,"SOAP_TRANSPORT_URI", "No transport URI was specified.");
   }
 
diff --git a/mozilla/extensions/webservices/soap/src/nsSOAPHeaderBlock.cpp b/mozilla/extensions/webservices/soap/src/nsSOAPHeaderBlock.cpp
index 8a03a42f45a..7fbabafa04c 100644
--- a/mozilla/extensions/webservices/soap/src/nsSOAPHeaderBlock.cpp
+++ b/mozilla/extensions/webservices/soap/src/nsSOAPHeaderBlock.cpp
@@ -102,7 +102,7 @@ NS_IMETHODIMP nsSOAPHeaderBlock::GetMustUnderstand(PRBool *
                        nsSOAPUtils::kMustUnderstandAttribute, m);
     if (NS_FAILED(rc))
       return rc;
-    if (m.Length() == 0)
+    if (m.IsEmpty())
       *aMustUnderstand = PR_FALSE;
     else if (m.Equals(nsSOAPUtils::kTrue)
              || m.Equals(nsSOAPUtils::kTrueA))
diff --git a/mozilla/extensions/xmlterm/base/mozLineTerm.cpp b/mozilla/extensions/xmlterm/base/mozLineTerm.cpp
index 503a54ca837..b7820ab6707 100644
--- a/mozilla/extensions/xmlterm/base/mozLineTerm.cpp
+++ b/mozilla/extensions/xmlterm/base/mozLineTerm.cpp
@@ -544,7 +544,7 @@ NS_IMETHODIMP mozLineTerm::Write(const PRUnichar *buf,
     nsAutoString timeStamp;
     result = mozXMLTermUtils::TimeStamp(60, mLastTime, timeStamp);
 
-    if (NS_SUCCEEDED(result) && (timeStamp.Length() > 0)) {
+    if (NS_SUCCEEDED(result) && !timeStamp.IsEmpty()) {
       char* temStr = ToNewCString(timeStamp);
       PR_LogPrint("<TS %s>\n", temStr);
       nsMemory::Free(temStr);
diff --git a/mozilla/extensions/xmlterm/base/mozXMLTermListeners.cpp b/mozilla/extensions/xmlterm/base/mozXMLTermListeners.cpp
index f75443b5471..e2e5838a4a4 100644
--- a/mozilla/extensions/xmlterm/base/mozXMLTermListeners.cpp
+++ b/mozilla/extensions/xmlterm/base/mozXMLTermListeners.cpp
@@ -390,7 +390,7 @@ mozXMLTermKeyListener::KeyPress(nsIDOMEvent* aKeyEvent)
     XMLT_LOG(mozXMLTermKeyListener::KeyPress,53,
              ("escPrefix=%d, keyChar=0x%x, \n", escPrefix, keyChar));
 
-    if (JSCommand.Length() > 0) {
+    if (!JSCommand.IsEmpty()) {
       // Execute JS command
       nsCOMPtr<nsIDOMDocument> domDocument;
       result = mXMLTerminal->GetDocument(getter_AddRefs(domDocument));
diff --git a/mozilla/extensions/xmlterm/base/mozXMLTermSession.cpp b/mozilla/extensions/xmlterm/base/mozXMLTermSession.cpp
index 236d65a7b52..77350a2acfc 100644
--- a/mozilla/extensions/xmlterm/base/mozXMLTermSession.cpp
+++ b/mozilla/extensions/xmlterm/base/mozXMLTermSession.cpp
@@ -986,7 +986,7 @@ NS_IMETHODIMP mozXMLTermSession::ReadAll(mozILineTermAux* lineTermAux,
               nsAutoString lsCommand;
               lsCommand.SetLength(0);
 
-              if (commandArgs.Length() > 0) {
+              if (!commandArgs.IsEmpty()) {
                 lsCommand.Append(NS_LITERAL_STRING("cd "));
                 lsCommand.Append(commandArgs);
                 lsCommand.Append(NS_LITERAL_STRING(";"));
@@ -1192,7 +1192,7 @@ NS_IMETHODIMP mozXMLTermSession::ExportHTML(const PRUnichar* aFilename,
 
   nsAutoString filename( aFilename );
 
-  if (filename.Length() == 0) {
+  if (filename.IsEmpty()) {
     // Write to STDERR
     char* htmlCString = ToNewCString(htmlString);
     fprintf(stderr, "mozXMLTermSession::ExportHTML:\n%s\n\n", htmlCString);
@@ -1365,7 +1365,7 @@ NS_IMETHODIMP mozXMLTermSession::DisplayInput(const nsString& aString,
   // Without this workaround, the cursor is positioned too close to the prompt
   // (i.e., too far to the left, ignoring the prompt whitespace)
 
-  if ((cursorCol > 0) || (mPromptHTML.Length() > 0)) {
+  if ((cursorCol > 0) || !mPromptHTML.IsEmpty()) {
     // Collapse selection to new cursor location
     result = selection->Collapse(mInputTextNode, cursorCol);
 
@@ -1655,7 +1655,7 @@ NS_IMETHODIMP mozXMLTermSession::BreakOutput(PRBool positionCursorBelow)
 
       mFragmentBuffer.SetLength(0);
 
-      if (jsOutput.Length() > 0) {
+      if (!jsOutput.IsEmpty()) {
         // Display JS output as HTML fragment
         result = InsertFragment(jsOutput, mOutputBlockNode,
                                 mCurrentEntryNumber);
@@ -1871,7 +1871,7 @@ NS_IMETHODIMP mozXMLTermSession::LimitOutputLines(PRBool deleteAllOld)
       attValue.SetLength(0);
       result = mozXMLTermUtils::GetNodeAttribute(nextChild, "class", attValue);
 
-      if (NS_FAILED(result)|| (attValue.Length() == 0)) {
+      if (NS_FAILED(result)|| attValue.IsEmpty())) {
         deleteNode = 1;
 
       } else {
@@ -2699,7 +2699,7 @@ NS_IMETHODIMP mozXMLTermSession::DeepSanitizeFragment(
 
       attValue.SetLength(0);
       result = domElement->GetAttribute(attName, attValue);
-      if (NS_SUCCEEDED(result) && (attValue.Length() > 0)) {
+      if (NS_SUCCEEDED(result) && !attValue.IsEmpty()) {
         // Save allowed event attribute value for re-insertion
         eventAttrVals[j] = attValue;
       }
@@ -2762,7 +2762,7 @@ NS_IMETHODIMP mozXMLTermSession::DeepSanitizeFragment(
       attValue.SetLength(0);
       result = domElement->GetAttribute(attName, attValue);
 
-      if (NS_SUCCEEDED(result) && (attValue.Length() > 0)) {
+      if (NS_SUCCEEDED(result) && !attValue.IsEmpty()) {
         // Modify attribute value
         SubstituteCommandNumber(attValue, entryNumber);
         domElement->SetAttribute(attName, attValue);
@@ -2775,7 +2775,7 @@ NS_IMETHODIMP mozXMLTermSession::DeepSanitizeFragment(
       attName.AppendWithConversion(sessionEventNames[j]);
       attValue = eventAttrVals[j];
 
-      if (attValue.Length() > 0) {
+      if (!attValue.IsEmpty()) {
         SubstituteCommandNumber(attValue, entryNumber);
 
         // Sanitize attribute value
@@ -2836,7 +2836,7 @@ NS_IMETHODIMP mozXMLTermSession::DeepRefreshEventHandlers(
     attValue.SetLength(0);
     result = domElement->GetAttribute(attName, attValue);
 
-    if (NS_SUCCEEDED(result) && (attValue.Length() > 0)) {
+    if (NS_SUCCEEDED(result) && !attValue.IsEmpty()) {
       // Refresh attribute value
       domElement->SetAttribute(attName, attValue);
     }
@@ -2904,7 +2904,7 @@ NS_IMETHODIMP mozXMLTermSession::FlushOutput(FlushActionType flushAction)
       // Clear incomplete PRE text
       mPreTextIncomplete.SetLength(0);
 
-      if ((mPreTextBufferLines == 0) && (mPreTextBuffered.Length() == 0)) {
+      if ((mPreTextBufferLines == 0) && mPreTextBuffered.IsEmpty()) {
         // Remove lone text node
         nsCOMPtr<nsIDOMNode> resultNode;
         result = mOutputDisplayNode->RemoveChild(mOutputTextNode,
@@ -2956,7 +2956,7 @@ NS_IMETHODIMP mozXMLTermSession::FlushOutput(FlushActionType flushAction)
       mOutputTextNode = nsnull;
 
       if ( (flushAction == SPLIT_INCOMPLETE_FLUSH) &&
-           (preTextSplit.Length() > 0) ) {
+           !preTextSplit.IsEmpty() ) {
         // Create new PRE element with incomplete text
         nsAutoString styleStr; styleStr.SetLength(0);
 
@@ -3334,7 +3334,7 @@ NS_IMETHODIMP mozXMLTermSession::NewEntry(const nsString& aPrompt)
 
   nsCOMPtr<nsIDOMNode> resultNode;
 
-  if (mPromptHTML.Length() == 0) {
+  if (mPromptHTML.IsEmpty()) {
 
 #define DEFAULT_ICON_PROMPT
 #ifdef DEFAULT_ICON_PROMPT    // Experimental code; has scrolling problems
@@ -3971,7 +3971,7 @@ NS_IMETHODIMP mozXMLTermSession::NewAnchor(const nsString& classAttribute,
   nsAutoString hrefVal(NS_LITERAL_STRING("#"));
   newElement->SetAttribute(hrefAtt, hrefVal);
 
-  if (classAttribute.Length() > 0) {
+  if (!classAttribute.IsEmpty()) {
     nsAutoString classStr(NS_LITERAL_STRING("class"));
     newElement->SetAttribute(classStr, classAttribute);
 
@@ -4028,7 +4028,7 @@ NS_IMETHODIMP mozXMLTermSession::NewElement(const nsString& tagName,
   if (NS_FAILED(result) || !newElement)
     return NS_ERROR_FAILURE;
 
-  if (name.Length() > 0) {
+  if (!name.IsEmpty()) {
     // Set attributes
     nsAutoString classAtt(NS_LITERAL_STRING("class"));
     nsAutoString classVal(name);
@@ -4164,19 +4164,19 @@ NS_IMETHODIMP mozXMLTermSession::NewIFrame(nsIDOMNode* parentNode,
   attValue.AppendInt(frameBorder,10);
   newElement->SetAttribute(attName, attValue);
 
-  if (src.Length() > 0) {
+  if (!src.IsEmpty()) {
     // Set SRC attribute
     attName.Assign(NS_LITERAL_STRING("src"));
     newElement->SetAttribute(attName, src);
   }
 
-  if (width.Length() > 0) {
+  if (!width.IsEmpty()) {
     // Set WIDTH attribute
     attName.Assign(NS_LITERAL_STRING("width"));
     newElement->SetAttribute(attName, width);
   }
 
-  if (height.Length() > 0) {
+  if (!height.IsEmpty()) {
     // Set HEIGHT attribute
     attName.Assign(NS_LITERAL_STRING("height"));
     newElement->SetAttribute(attName, height);
@@ -4379,7 +4379,7 @@ NS_IMETHODIMP mozXMLTermSession::ToHTMLString(nsIDOMNode* aNode,
                 }
 
                 result = attr->GetValue(attrValue);
-                if (NS_SUCCEEDED(result) && (attrName.Length() > 0)) {
+                if (NS_SUCCEEDED(result) && !attrName.IsEmpty()) {
                   htmlString.Append(NS_LITERAL_STRING("=\""));
                   htmlString.Append(attrValue);
                   htmlString.Append(NS_LITERAL_STRING("\""));
@@ -4412,7 +4412,7 @@ NS_IMETHODIMP mozXMLTermSession::ToHTMLString(nsIDOMNode* aNode,
             break;
         }
 
-        if (htmlInner.Length() > 0) {
+        if (!htmlInner.IsEmpty()) {
           if (insidePRENode)
             htmlString.Append(NS_LITERAL_STRING("\n>"));
           else
@@ -4587,7 +4587,7 @@ void mozXMLTermSession::TraverseDOMTree(FILE* fileStream,
 	  attValue.SetLength(0);
 
           result = domElement->GetAttribute(attName, attValue);
-          if (NS_SUCCEEDED(result) && (attValue.Length() > 0)) {
+          if (NS_SUCCEEDED(result) && !attValue.IsEmpty()) {
             // Print attribute value
             char* tagCString2 = ToNewCString(attValue);
             fprintf(fileStream, " %s=%s", printAttributeNames[j], tagCString2);
diff --git a/mozilla/gfx/src/mac/nsDeviceContextMac.cpp b/mozilla/gfx/src/mac/nsDeviceContextMac.cpp
index 859ef43f5a2..c2fd50d23c3 100644
--- a/mozilla/gfx/src/mac/nsDeviceContextMac.cpp
+++ b/mozilla/gfx/src/mac/nsDeviceContextMac.cpp
@@ -373,8 +373,8 @@ NS_IMETHODIMP nsDeviceContextMac :: GetSystemFont(nsSystemFontID aID, nsFont *aF
                ::TECDisposeConverter(converter);
            }             
         }
-        NS_ASSERTION(aFont->name.Length() > 0, "empty font name");
-        if (aFont->name.Length()  == 0) 
+        NS_ASSERTION(!aFont->name.IsEmpty(), "empty font name");
+        if (aFont->name.IsEmpty()) 
         {
            aFont->name.AssignWithConversion( (char*)&fontName[1], fontName[0] );
         }
diff --git a/mozilla/gfx/src/nsDeviceContext.cpp b/mozilla/gfx/src/nsDeviceContext.cpp
index c19cc0138a5..c4be6c7bb3f 100644
--- a/mozilla/gfx/src/nsDeviceContext.cpp
+++ b/mozilla/gfx/src/nsDeviceContext.cpp
@@ -526,7 +526,7 @@ nsresult DeviceContextImpl::AliasFont(const nsString& aFont,
           result = NS_ERROR_OUT_OF_MEMORY;
         }
       }
-      else if ((0 < aAltAlias.Length()) && NS_SUCCEEDED(CheckFontExistence(aAltAlias))) {
+      else if (!aAltAlias.IsEmpty() && NS_SUCCEEDED(CheckFontExistence(aAltAlias))) {
         nsString* entry = new nsString(aAltAlias);
         if (nsnull != entry) {
           FontAliasKey key(aFont);
diff --git a/mozilla/gfx/src/nsFont.cpp b/mozilla/gfx/src/nsFont.cpp
index 5923ad16799..7289f96d8b2 100644
--- a/mozilla/gfx/src/nsFont.cpp
+++ b/mozilla/gfx/src/nsFont.cpp
@@ -178,12 +178,12 @@ PRBool nsFont::EnumerateFamilies(nsFontFamilyEnumFunc aFunc, void* aData) const
 
     if (PR_FALSE == quoted) {
       familyStr.CompressWhitespace(PR_FALSE, PR_TRUE);
-      if (0 < familyStr.Length()) {
+      if (!familyStr.IsEmpty()) {
         generic = IsGenericFontFamily(familyStr);
       }
     }
 
-    if (0 < familyStr.Length()) {
+    if (!familyStr.IsEmpty()) {
       running = (*aFunc)(familyStr, generic, aData);
     }
 
diff --git a/mozilla/gfx/src/nsPrintOptionsImpl.cpp b/mozilla/gfx/src/nsPrintOptionsImpl.cpp
index cd82810ee32..2281513aa9c 100644
--- a/mozilla/gfx/src/nsPrintOptionsImpl.cpp
+++ b/mozilla/gfx/src/nsPrintOptionsImpl.cpp
@@ -231,7 +231,7 @@ NS_IMETHODIMP nsPrinterListEnumerator::GetNext(nsISupports **aPrinter)
 NS_IMETHODIMP 
 nsPrintOptions::SetFontNamePointSize(nsString& aFontName, PRInt32 aPointSize)
 {
-  if (sDefaultFont != nsnull && aFontName.Length() > 0 && aPointSize > 0) {
+  if (sDefaultFont != nsnull && !aFontName.IsEmpty() && aPointSize > 0) {
     sDefaultFont->name = aFontName;
     sDefaultFont->size = NSIntPointsToTwips(aPointSize);
   }
diff --git a/mozilla/gfx/src/nsPrintSettingsImpl.cpp b/mozilla/gfx/src/nsPrintSettingsImpl.cpp
index 3c65182f736..baced5ea7fe 100644
--- a/mozilla/gfx/src/nsPrintSettingsImpl.cpp
+++ b/mozilla/gfx/src/nsPrintSettingsImpl.cpp
@@ -442,7 +442,7 @@ NS_IMETHODIMP nsPrintSettings::SetPrintRange(PRInt16 aPrintRange)
 NS_IMETHODIMP nsPrintSettings::GetTitle(PRUnichar * *aTitle)
 {
   NS_ENSURE_ARG_POINTER(aTitle);
-  if (mTitle.Length() > 0) {
+  if (!mTitle.IsEmpty()) {
     *aTitle = ToNewUnicode(mTitle);
   } else {
     *aTitle = nsnull;
@@ -463,7 +463,7 @@ NS_IMETHODIMP nsPrintSettings::SetTitle(const PRUnichar * aTitle)
 NS_IMETHODIMP nsPrintSettings::GetDocURL(PRUnichar * *aDocURL)
 {
   NS_ENSURE_ARG_POINTER(aDocURL);
-  if (mURL.Length() > 0) {
+  if (!mURL.IsEmpty()) {
     *aDocURL = ToNewUnicode(mURL);
   } else {
     *aDocURL = nsnull;
@@ -694,7 +694,7 @@ NS_IMETHODIMP nsPrintSettings::SetShowPrintProgress(PRBool aShowPrintProgress)
 NS_IMETHODIMP nsPrintSettings::GetPaperName(PRUnichar * *aPaperName)
 {
   NS_ENSURE_ARG_POINTER(aPaperName);
-  if (mPaperName.Length()) {
+  if (!mPaperName.IsEmpty()) {
     *aPaperName = ToNewUnicode(mPaperName);
   } else {
     *aPaperName = nsnull;
diff --git a/mozilla/gfx/src/os2/nsFontMetricsOS2.cpp b/mozilla/gfx/src/os2/nsFontMetricsOS2.cpp
index 46c3e108c7a..0fd7457163b 100644
--- a/mozilla/gfx/src/os2/nsFontMetricsOS2.cpp
+++ b/mozilla/gfx/src/os2/nsFontMetricsOS2.cpp
@@ -993,7 +993,7 @@ AppendGenericFontFromPref(nsString& aFontname,
   MAKE_FONT_PREF_KEY(pref, "font.name.", generic_dot_langGroup);
   res = gPref->CopyUnicharPref(pref.get(), getter_Copies(value));      
   if (NS_SUCCEEDED(res)) {
-    if(aFontname.Length() > 0)
+    if(!aFontname.IsEmpty())
       aFontname.Append((PRUnichar)',');
     aFontname.Append(value);
   }
@@ -1003,7 +1003,7 @@ AppendGenericFontFromPref(nsString& aFontname,
   MAKE_FONT_PREF_KEY(pref, "font.name-list.", generic_dot_langGroup);
   res = gPref->CopyUnicharPref(pref.get(), getter_Copies(value));      
   if (NS_SUCCEEDED(res)) {
-    if(aFontname.Length() > 0)
+    if(!aFontname.IsEmpty())
       aFontname.Append((PRUnichar)',');
     aFontname.Append(value);
   }
diff --git a/mozilla/gfx/src/ps/nsFontMetricsPS.cpp b/mozilla/gfx/src/ps/nsFontMetricsPS.cpp
index 7d6562a5ced..1cb593ed7e5 100644
--- a/mozilla/gfx/src/ps/nsFontMetricsPS.cpp
+++ b/mozilla/gfx/src/ps/nsFontMetricsPS.cpp
@@ -1607,7 +1607,7 @@ void nsFT2Type8Generator::GeneratePSFont(FILE* aFile)
     return;
  
   int wmode = 0;
-  if (mSubset.Length() > 0)
+  if (!mSubset.IsEmpty())
     FT2SubsetToType8(face, mSubset.get(), mSubset.Length(), wmode, aFile);
 }
 #endif //MOZ_ENABLE_FREETYPE2
diff --git a/mozilla/gfx/src/windows/nsDeviceContextWin.cpp b/mozilla/gfx/src/windows/nsDeviceContextWin.cpp
index 91b8093451f..892bdd9e6bf 100644
--- a/mozilla/gfx/src/windows/nsDeviceContextWin.cpp
+++ b/mozilla/gfx/src/windows/nsDeviceContextWin.cpp
@@ -788,7 +788,7 @@ NS_IMETHODIMP nsDeviceContextWin :: BeginDocument(PRUnichar * aTitle, PRUnichar*
 
     char* docName = nsnull;
     nsAutoString str(aPrintToFileName);
-    if (str.Length() > 0) {
+    if (!str.IsEmpty()) {
       docName = ToNewCString(str);
     }
     docinfo.cbSize = sizeof(docinfo);
diff --git a/mozilla/gfx/src/windows/nsFontMetricsWin.cpp b/mozilla/gfx/src/windows/nsFontMetricsWin.cpp
index a360d81e39a..20e45d1e5fa 100644
--- a/mozilla/gfx/src/windows/nsFontMetricsWin.cpp
+++ b/mozilla/gfx/src/windows/nsFontMetricsWin.cpp
@@ -3300,7 +3300,7 @@ AppendGenericFontFromPref(nsString& aFontname,
   MAKE_FONT_PREF_KEY(pref, "font.name.", generic_dot_langGroup);
   res = gPref->CopyUnicharPref(pref.get(), getter_Copies(value));      
   if (NS_SUCCEEDED(res)) {
-    if(aFontname.Length() > 0)
+    if(!aFontname.IsEmpty())
       aFontname.Append((PRUnichar)',');
     aFontname.Append(value);
   }
@@ -3310,7 +3310,7 @@ AppendGenericFontFromPref(nsString& aFontname,
   MAKE_FONT_PREF_KEY(pref, "font.name-list.", generic_dot_langGroup);
   res = gPref->CopyUnicharPref(pref.get(), getter_Copies(value));      
   if (NS_SUCCEEDED(res)) {
-    if(aFontname.Length() > 0)
+    if(!aFontname.IsEmpty())
       aFontname.Append((PRUnichar)',');
     aFontname.Append(value);
   }
diff --git a/mozilla/htmlparser/src/nsExpatDriver.cpp b/mozilla/htmlparser/src/nsExpatDriver.cpp
index 5461f7ebc0d..711e426b17e 100644
--- a/mozilla/htmlparser/src/nsExpatDriver.cpp
+++ b/mozilla/htmlparser/src/nsExpatDriver.cpp
@@ -956,7 +956,7 @@ nsExpatDriver::CanParse(CParserContext& aParserContext,
       result=ePrimaryDetect;
     }
     else {
-      if (0 == aParserContext.mMimeType.Length() &&
+      if (aParserContext.mMimeType.IsEmpty() &&
           kNotFound != aBuffer.Find("<?xml ")) {
         aParserContext.SetMimeType(NS_LITERAL_CSTRING(kXMLTextContentType));
         result=eValidDetect;
diff --git a/mozilla/htmlparser/src/nsLoggingSink.cpp b/mozilla/htmlparser/src/nsLoggingSink.cpp
index ced60b94341..31b77588a35 100644
--- a/mozilla/htmlparser/src/nsLoggingSink.cpp
+++ b/mozilla/htmlparser/src/nsLoggingSink.cpp
@@ -609,7 +609,7 @@ nsLoggingSink::WriteAttributes(const nsIParserNode& aNode) {
  
     tmp.Truncate();
     tmp.Append(v);
-    if(tmp.Length() > 0) {
+    if(!tmp.IsEmpty()) {
       PRUnichar first = tmp.First();
       if ((first == '"') || (first == '\'')) {
         if (tmp.Last() == first) {
@@ -669,7 +669,7 @@ nsLoggingSink::WillWriteAttributes(const nsIParserNode& aNode)
     PRInt32 lineNo = 0;
 
     dtd->CollectSkippedContent(aNode.GetNodeType(), content, lineNo);
-    if (content.Length() > 0) {
+    if (!content.IsEmpty()) {
       return PR_TRUE;
     }
   }
@@ -778,7 +778,7 @@ nsLoggingSink::GetNewCString(const nsAString& aValue, char** aResult)
   nsAutoString temp;
   result=QuoteText(aValue,temp);
   if(NS_SUCCEEDED(result)) {
-    if(temp.Length()>0) {
+    if(!temp.IsEmpty()) {
       *aResult = ToNewCString(temp);
     }
   }
diff --git a/mozilla/htmlparser/src/nsParser.cpp b/mozilla/htmlparser/src/nsParser.cpp
index 2075731e705..b55ea8e9364 100644
--- a/mozilla/htmlparser/src/nsParser.cpp
+++ b/mozilla/htmlparser/src/nsParser.cpp
@@ -1567,7 +1567,7 @@ nsParser::Parse(const nsAString& aSourceBuffer,
 
   nsresult result=NS_OK;
 
-  if(aLastCall && (0==aSourceBuffer.Length())) {
+  if(aLastCall && aSourceBuffer.IsEmpty()) {
     // Nothing is being passed to the parser so return
     // immediately. mUnusedInput will get processed when
     // some data is actually passed in.
@@ -1583,7 +1583,7 @@ nsParser::Parse(const nsAString& aSourceBuffer,
   // till we're completely done. 
   nsCOMPtr<nsIParser> kungFuDeathGrip(this);
 
-  if(aSourceBuffer.Length() || mUnusedInput.Length()) { 
+  if(!aSourceBuffer.IsEmpty() || !mUnusedInput.IsEmpty()) {
     
     if (aVerifyEnabled) {
       mFlags |= NS_PARSER_FLAG_DTD_VERIFICATION;
@@ -1747,7 +1747,7 @@ nsresult nsParser::ResumeParse(PRBool allowIteration, PRBool aIsFinalChunk, PRBo
        
       while((result==NS_OK) && (theIterationIsOk)) {
         theFirstTime=PR_FALSE;
-        if(mUnusedInput.Length()>0) {
+        if(!mUnusedInput.IsEmpty()) {
           if(mParserContext->mScanner) {
             // -- Ref: Bug# 22485 --
             // Insert the unused input into the source buffer 
@@ -2163,7 +2163,7 @@ static PRBool DetectByteOrderMark(const unsigned char* aBytes, PRInt32 aLen, nsS
    // }
    // break;
  }  // switch
- return oCharset.Length() > 0;
+ return !oCharset.IsEmpty();
 }
 
 inline const char GetNextChar(nsACString::const_iterator& aStart,
diff --git a/mozilla/layout/base/nsFrameManager.cpp b/mozilla/layout/base/nsFrameManager.cpp
index 5cf865da09f..469526c6858 100644
--- a/mozilla/layout/base/nsFrameManager.cpp
+++ b/mozilla/layout/base/nsFrameManager.cpp
@@ -1608,7 +1608,7 @@ HasAttributeContent(nsStyleContext* aStyleContext,
           PRInt32 error;
           attrNameSpace = nameSpaceVal.ToInteger(&error, 10);
           contentString.Cut(0, barIndex + 1);
-          if (contentString.Length()) {
+          if (!contentString.IsEmpty()) {
             attrName = NS_NewAtom(contentString);
           }
         }
@@ -1773,7 +1773,7 @@ FrameManager::ReResolveStyleContext(nsIPresContext* aPresContext,
         const nsStyleBackground* oldColor = oldContext->GetStyleBackground();
         const nsStyleBackground* newColor = newContext->GetStyleBackground();
 
-        if (oldColor->mBackgroundImage.Length() > 0 &&
+        if (!oldColor->mBackgroundImage.IsEmpty() &&
             oldColor->mBackgroundImage != newColor->mBackgroundImage) {
           // stop the image loading for the frame, the image has changed
           aPresContext->StopImagesFor(aFrame);
diff --git a/mozilla/layout/base/nsPresShell.cpp b/mozilla/layout/base/nsPresShell.cpp
index 90d6057ba77..c411b9b9692 100644
--- a/mozilla/layout/base/nsPresShell.cpp
+++ b/mozilla/layout/base/nsPresShell.cpp
@@ -1991,7 +1991,7 @@ PresShell::GetActiveAlternateStyleSheet(nsString& aSheetTitle)
         if (PR_FALSE == type.Equals(textHtml)) {
           nsAutoString title;
           sheet->GetTitle(title);
-          if (0 < title.Length()) {
+          if (!title.IsEmpty()) {
             aSheetTitle = title;
             index = count;  // stop looking
           }
@@ -2060,7 +2060,7 @@ PresShell::ListAlternateStyleSheets(nsStringArray& aTitleList)
         if (PR_FALSE == type.Equals(textHtml)) {
           nsAutoString  title;
           sheet->GetTitle(title);
-          if (0 < title.Length()) {
+          if (!title.IsEmpty()) {
             if (-1 == aTitleList.IndexOf(title)) {
               aTitleList.AppendString(title);
             }
diff --git a/mozilla/layout/forms/nsComboboxControlFrame.cpp b/mozilla/layout/forms/nsComboboxControlFrame.cpp
index 388a11be86d..68eef45f445 100644
--- a/mozilla/layout/forms/nsComboboxControlFrame.cpp
+++ b/mozilla/layout/forms/nsComboboxControlFrame.cpp
@@ -867,7 +867,7 @@ nsComboboxControlFrame::ReflowItems(nsIPresContext* aPresContext,
       if (optionElement) {
         nsAutoString text;
         rv = optionElement->GetLabel(text);
-        if (NS_CONTENT_ATTR_HAS_VALUE != rv || 0 == text.Length()) {
+        if (NS_CONTENT_ATTR_HAS_VALUE != rv || text.IsEmpty()) {
           if (NS_OK == optionElement->GetText(text)) {
             nscoord width;
             aReflowState.rendContext->GetWidth(text, width);
@@ -1928,7 +1928,7 @@ nsComboboxControlFrame::RedisplayText(PRInt32 aIndex)
       fragment->AppendTo(value);
     }
     PRBool shouldSetValue = PR_FALSE;
-    if (NS_FAILED(result) || value.Length() == 0) {
+    if (NS_FAILED(result) || value.IsEmpty()) {
       shouldSetValue = PR_TRUE;
     } else {
        shouldSetValue = value != textToDisplay;
diff --git a/mozilla/layout/forms/nsGfxCheckboxControlFrame.cpp b/mozilla/layout/forms/nsGfxCheckboxControlFrame.cpp
index 0ed1d5be794..dba59377cd3 100644
--- a/mozilla/layout/forms/nsGfxCheckboxControlFrame.cpp
+++ b/mozilla/layout/forms/nsGfxCheckboxControlFrame.cpp
@@ -231,7 +231,7 @@ nsGfxCheckboxControlFrame::Paint(nsIPresContext*   aPresContext,
     if (!mCheckButtonFaceStyle && GetCheckboxState()) {
       const nsStyleBackground* myColor = mCheckButtonFaceStyle->GetStyleBackground();
 
-      if (myColor->mBackgroundImage.Length() > 0) {
+      if (!myColor->mBackgroundImage.IsEmpty()) {
         const nsStyleBorder* myBorder = mCheckButtonFaceStyle->GetStyleBorder();
         const nsStylePadding* myPadding = mCheckButtonFaceStyle->GetStylePadding();
         const nsStylePosition* myPosition = mCheckButtonFaceStyle->GetStylePosition();
diff --git a/mozilla/layout/forms/nsIsIndexFrame.cpp b/mozilla/layout/forms/nsIsIndexFrame.cpp
index 060acd9cef9..83d96e8ff0a 100644
--- a/mozilla/layout/forms/nsIsIndexFrame.cpp
+++ b/mozilla/layout/forms/nsIsIndexFrame.cpp
@@ -156,7 +156,7 @@ nsIsIndexFrame::UpdatePromptLabel()
       }
     }
   }
-  if (prompt.Length() == 0) {
+  if (prompt.IsEmpty()) {
     // Generate localized label.
     // We can't make any assumption as to what the default would be
     // because the value is localized for non-english platforms, thus
diff --git a/mozilla/layout/forms/nsListControlFrame.cpp b/mozilla/layout/forms/nsListControlFrame.cpp
index 27a37283a9d..17edecd6876 100644
--- a/mozilla/layout/forms/nsListControlFrame.cpp
+++ b/mozilla/layout/forms/nsListControlFrame.cpp
@@ -2194,15 +2194,15 @@ nsListControlFrame::GetOptionText(PRInt32 aIndex, nsAString & aStr)
         rv = optionElement->GetLabel(text);
         // the return value is always NS_OK from DOMElements
         // it is meaningless to check for it
-        if (text.Length() > 0) { 
+        if (!text.IsEmpty()) { 
           nsAutoString compressText = text;
           compressText.CompressWhitespace(PR_TRUE, PR_TRUE);
-          if (compressText.Length() != 0) {
+          if (!compressText.IsEmpty()) {
             text = compressText;
           }
         }
 
-        if (0 == text.Length()) {
+        if (text.IsEmpty()) {
           // the return value is always NS_OK from DOMElements
           // it is meaningless to check for it
           optionElement->GetText(text);
diff --git a/mozilla/layout/generic/nsFrameFrame.cpp b/mozilla/layout/generic/nsFrameFrame.cpp
index c78628b1280..8986d42e902 100644
--- a/mozilla/layout/generic/nsFrameFrame.cpp
+++ b/mozilla/layout/generic/nsFrameFrame.cpp
@@ -772,11 +772,11 @@ PRBool nsHTMLFrameInnerFrame::GetURL(nsIContent* aContent, nsString& aResult)
 
   if (type.get() == nsHTMLAtoms::object) {
     if (NS_CONTENT_ATTR_HAS_VALUE == (aContent->GetAttr(kNameSpaceID_None, nsHTMLAtoms::data, aResult)))
-      if (aResult.Length() > 0)
+      if (!aResult.IsEmpty())
         return PR_TRUE;
   }else
     if (NS_CONTENT_ATTR_HAS_VALUE == (aContent->GetAttr(kNameSpaceID_None, nsHTMLAtoms::src, aResult)))
-      if (aResult.Length() > 0)
+      if (!aResult.IsEmpty())
         return PR_TRUE;
 
   return PR_FALSE;
@@ -787,7 +787,7 @@ PRBool nsHTMLFrameInnerFrame::GetName(nsIContent* aContent, nsString& aResult)
   aResult.SetLength(0);
 
   if (NS_CONTENT_ATTR_HAS_VALUE == (aContent->GetAttr(kNameSpaceID_None, nsHTMLAtoms::name, aResult))) {
-    if (aResult.Length() > 0) {
+    if (!aResult.IsEmpty()) {
       return PR_TRUE;
     }
   }
diff --git a/mozilla/layout/generic/nsImageFrame.cpp b/mozilla/layout/generic/nsImageFrame.cpp
index db9e9cd4c65..b5710fa6d31 100644
--- a/mozilla/layout/generic/nsImageFrame.cpp
+++ b/mozilla/layout/generic/nsImageFrame.cpp
@@ -1606,7 +1606,7 @@ nsImageFrame::GetAnchorHREFAndTarget(nsString& aHref, nsString& aTarget)
     nsCOMPtr<nsIDOMHTMLAnchorElement> anchor(do_QueryInterface(content));
     if (anchor) {
       anchor->GetHref(aHref);
-      if (aHref.Length() > 0) {
+      if (!aHref.IsEmpty()) {
         status = PR_TRUE;
       }
       anchor->GetTarget(aTarget);
diff --git a/mozilla/layout/generic/nsImageMap.cpp b/mozilla/layout/generic/nsImageMap.cpp
index 671778936e8..3fe1a6db189 100644
--- a/mozilla/layout/generic/nsImageMap.cpp
+++ b/mozilla/layout/generic/nsImageMap.cpp
@@ -916,7 +916,7 @@ nsImageMap::AddArea(nsIContent* aArea)
   frameManager->SetPrimaryFrameFor(aArea, mImageFrame);
 
   Area* area;
-  if ((0 == shape.Length()) ||
+  if (shape.IsEmpty() ||
       shape.EqualsIgnoreCase("rect") ||
       shape.EqualsIgnoreCase("rectangle")) {
     area = new RectArea(aArea, hasURL);
@@ -994,7 +994,7 @@ nsImageMap::IsInside(nscoord aX, nscoord aY) const
     if (area->IsInside(aX, aY)) {
       nsAutoString href;
       area->GetHREF(href);
-      if (href.Length() > 0) {
+      if (!href.IsEmpty()) {
         return PR_TRUE;
       }
       else {
diff --git a/mozilla/layout/generic/nsObjectFrame.cpp b/mozilla/layout/generic/nsObjectFrame.cpp
index f2bbfafb8b3..efb9ea8c09d 100644
--- a/mozilla/layout/generic/nsObjectFrame.cpp
+++ b/mozilla/layout/generic/nsObjectFrame.cpp
@@ -576,7 +576,7 @@ void nsObjectFrame::IsSupportedDocument(nsIContent* aContent, PRBool* aDoc)
     nsXPIDLCString value;
     rv = catman->GetCategoryEntry("Gecko-Content-Viewers",contentType, getter_Copies(value));
 
-    if (NS_SUCCEEDED(rv) && value && *value && (value.Length() > 0))
+    if (NS_SUCCEEDED(rv) && !value.IsEmpty())
       *aDoc = PR_TRUE;
 
     if (contentType)
@@ -1158,7 +1158,7 @@ nsObjectFrame::Reflow(nsIPresContext*          aPresContext,
 
         // now try to instantiate a plugin instance based on a mime type
         const char* mimeType = mimeTypeStr.get();
-        if (mimeType || (src.Length() > 0)) {
+        if (mimeType || !src.IsEmpty()) {
           if (!mimeType) {
             // we don't have a mime type, try to figure it out from extension
             nsXPIDLCString extension;
@@ -3015,7 +3015,7 @@ nsresult nsPluginInstanceOwner::EnsureCachedAttrParamArrays()
         // let's NOT count up param tags that don't have a name attribute
         nsAutoString name;
         domelement->GetAttribute(NS_LITERAL_STRING("name"), name);
-        if (name.Length() > 0) {
+        if (!name.IsEmpty()) {
           nsCOMPtr<nsIDOMNode> parent;
           nsCOMPtr<nsIDOMHTMLObjectElement> domobject;
           nsCOMPtr<nsIDOMHTMLAppletElement> domapplet;
diff --git a/mozilla/layout/generic/nsPageFrame.cpp b/mozilla/layout/generic/nsPageFrame.cpp
index 12afd3b3b05..a611cc44268 100644
--- a/mozilla/layout/generic/nsPageFrame.cpp
+++ b/mozilla/layout/generic/nsPageFrame.cpp
@@ -510,7 +510,7 @@ nsPageFrame::DrawHeaderFooter(nsIPresContext*      aPresContext,
 
   // first make sure we have a vaild string and that the height of the
   // text will fit in the margin
-  if (aStr.Length() > 0 && 
+  if (!aStr.IsEmpty() && 
       ((aHeaderFooter == eHeader && aHeight < mMargin.top) ||
        (aHeaderFooter == eFooter && aHeight < mMargin.bottom))) {
     nsAutoString str;
diff --git a/mozilla/layout/html/base/src/nsFrameManager.cpp b/mozilla/layout/html/base/src/nsFrameManager.cpp
index 5cf865da09f..469526c6858 100644
--- a/mozilla/layout/html/base/src/nsFrameManager.cpp
+++ b/mozilla/layout/html/base/src/nsFrameManager.cpp
@@ -1608,7 +1608,7 @@ HasAttributeContent(nsStyleContext* aStyleContext,
           PRInt32 error;
           attrNameSpace = nameSpaceVal.ToInteger(&error, 10);
           contentString.Cut(0, barIndex + 1);
-          if (contentString.Length()) {
+          if (!contentString.IsEmpty()) {
             attrName = NS_NewAtom(contentString);
           }
         }
@@ -1773,7 +1773,7 @@ FrameManager::ReResolveStyleContext(nsIPresContext* aPresContext,
         const nsStyleBackground* oldColor = oldContext->GetStyleBackground();
         const nsStyleBackground* newColor = newContext->GetStyleBackground();
 
-        if (oldColor->mBackgroundImage.Length() > 0 &&
+        if (!oldColor->mBackgroundImage.IsEmpty() &&
             oldColor->mBackgroundImage != newColor->mBackgroundImage) {
           // stop the image loading for the frame, the image has changed
           aPresContext->StopImagesFor(aFrame);
diff --git a/mozilla/layout/html/base/src/nsImageFrame.cpp b/mozilla/layout/html/base/src/nsImageFrame.cpp
index db9e9cd4c65..b5710fa6d31 100644
--- a/mozilla/layout/html/base/src/nsImageFrame.cpp
+++ b/mozilla/layout/html/base/src/nsImageFrame.cpp
@@ -1606,7 +1606,7 @@ nsImageFrame::GetAnchorHREFAndTarget(nsString& aHref, nsString& aTarget)
     nsCOMPtr<nsIDOMHTMLAnchorElement> anchor(do_QueryInterface(content));
     if (anchor) {
       anchor->GetHref(aHref);
-      if (aHref.Length() > 0) {
+      if (!aHref.IsEmpty()) {
         status = PR_TRUE;
       }
       anchor->GetTarget(aTarget);
diff --git a/mozilla/layout/html/base/src/nsImageMap.cpp b/mozilla/layout/html/base/src/nsImageMap.cpp
index 671778936e8..3fe1a6db189 100644
--- a/mozilla/layout/html/base/src/nsImageMap.cpp
+++ b/mozilla/layout/html/base/src/nsImageMap.cpp
@@ -916,7 +916,7 @@ nsImageMap::AddArea(nsIContent* aArea)
   frameManager->SetPrimaryFrameFor(aArea, mImageFrame);
 
   Area* area;
-  if ((0 == shape.Length()) ||
+  if (shape.IsEmpty() ||
       shape.EqualsIgnoreCase("rect") ||
       shape.EqualsIgnoreCase("rectangle")) {
     area = new RectArea(aArea, hasURL);
@@ -994,7 +994,7 @@ nsImageMap::IsInside(nscoord aX, nscoord aY) const
     if (area->IsInside(aX, aY)) {
       nsAutoString href;
       area->GetHREF(href);
-      if (href.Length() > 0) {
+      if (!href.IsEmpty()) {
         return PR_TRUE;
       }
       else {
diff --git a/mozilla/layout/html/base/src/nsObjectFrame.cpp b/mozilla/layout/html/base/src/nsObjectFrame.cpp
index f2bbfafb8b3..efb9ea8c09d 100644
--- a/mozilla/layout/html/base/src/nsObjectFrame.cpp
+++ b/mozilla/layout/html/base/src/nsObjectFrame.cpp
@@ -576,7 +576,7 @@ void nsObjectFrame::IsSupportedDocument(nsIContent* aContent, PRBool* aDoc)
     nsXPIDLCString value;
     rv = catman->GetCategoryEntry("Gecko-Content-Viewers",contentType, getter_Copies(value));
 
-    if (NS_SUCCEEDED(rv) && value && *value && (value.Length() > 0))
+    if (NS_SUCCEEDED(rv) && !value.IsEmpty())
       *aDoc = PR_TRUE;
 
     if (contentType)
@@ -1158,7 +1158,7 @@ nsObjectFrame::Reflow(nsIPresContext*          aPresContext,
 
         // now try to instantiate a plugin instance based on a mime type
         const char* mimeType = mimeTypeStr.get();
-        if (mimeType || (src.Length() > 0)) {
+        if (mimeType || !src.IsEmpty()) {
           if (!mimeType) {
             // we don't have a mime type, try to figure it out from extension
             nsXPIDLCString extension;
@@ -3015,7 +3015,7 @@ nsresult nsPluginInstanceOwner::EnsureCachedAttrParamArrays()
         // let's NOT count up param tags that don't have a name attribute
         nsAutoString name;
         domelement->GetAttribute(NS_LITERAL_STRING("name"), name);
-        if (name.Length() > 0) {
+        if (!name.IsEmpty()) {
           nsCOMPtr<nsIDOMNode> parent;
           nsCOMPtr<nsIDOMHTMLObjectElement> domobject;
           nsCOMPtr<nsIDOMHTMLAppletElement> domapplet;
diff --git a/mozilla/layout/html/base/src/nsPageFrame.cpp b/mozilla/layout/html/base/src/nsPageFrame.cpp
index 12afd3b3b05..a611cc44268 100644
--- a/mozilla/layout/html/base/src/nsPageFrame.cpp
+++ b/mozilla/layout/html/base/src/nsPageFrame.cpp
@@ -510,7 +510,7 @@ nsPageFrame::DrawHeaderFooter(nsIPresContext*      aPresContext,
 
   // first make sure we have a vaild string and that the height of the
   // text will fit in the margin
-  if (aStr.Length() > 0 && 
+  if (!aStr.IsEmpty() && 
       ((aHeaderFooter == eHeader && aHeight < mMargin.top) ||
        (aHeaderFooter == eFooter && aHeight < mMargin.bottom))) {
     nsAutoString str;
diff --git a/mozilla/layout/html/base/src/nsPresShell.cpp b/mozilla/layout/html/base/src/nsPresShell.cpp
index 90d6057ba77..c411b9b9692 100644
--- a/mozilla/layout/html/base/src/nsPresShell.cpp
+++ b/mozilla/layout/html/base/src/nsPresShell.cpp
@@ -1991,7 +1991,7 @@ PresShell::GetActiveAlternateStyleSheet(nsString& aSheetTitle)
         if (PR_FALSE == type.Equals(textHtml)) {
           nsAutoString title;
           sheet->GetTitle(title);
-          if (0 < title.Length()) {
+          if (!title.IsEmpty()) {
             aSheetTitle = title;
             index = count;  // stop looking
           }
@@ -2060,7 +2060,7 @@ PresShell::ListAlternateStyleSheets(nsStringArray& aTitleList)
         if (PR_FALSE == type.Equals(textHtml)) {
           nsAutoString  title;
           sheet->GetTitle(title);
-          if (0 < title.Length()) {
+          if (!title.IsEmpty()) {
             if (-1 == aTitleList.IndexOf(title)) {
               aTitleList.AppendString(title);
             }
diff --git a/mozilla/layout/html/document/src/nsFrameFrame.cpp b/mozilla/layout/html/document/src/nsFrameFrame.cpp
index c78628b1280..8986d42e902 100644
--- a/mozilla/layout/html/document/src/nsFrameFrame.cpp
+++ b/mozilla/layout/html/document/src/nsFrameFrame.cpp
@@ -772,11 +772,11 @@ PRBool nsHTMLFrameInnerFrame::GetURL(nsIContent* aContent, nsString& aResult)
 
   if (type.get() == nsHTMLAtoms::object) {
     if (NS_CONTENT_ATTR_HAS_VALUE == (aContent->GetAttr(kNameSpaceID_None, nsHTMLAtoms::data, aResult)))
-      if (aResult.Length() > 0)
+      if (!aResult.IsEmpty())
         return PR_TRUE;
   }else
     if (NS_CONTENT_ATTR_HAS_VALUE == (aContent->GetAttr(kNameSpaceID_None, nsHTMLAtoms::src, aResult)))
-      if (aResult.Length() > 0)
+      if (!aResult.IsEmpty())
         return PR_TRUE;
 
   return PR_FALSE;
@@ -787,7 +787,7 @@ PRBool nsHTMLFrameInnerFrame::GetName(nsIContent* aContent, nsString& aResult)
   aResult.SetLength(0);
 
   if (NS_CONTENT_ATTR_HAS_VALUE == (aContent->GetAttr(kNameSpaceID_None, nsHTMLAtoms::name, aResult))) {
-    if (aResult.Length() > 0) {
+    if (!aResult.IsEmpty()) {
       return PR_TRUE;
     }
   }
diff --git a/mozilla/layout/html/forms/src/nsComboboxControlFrame.cpp b/mozilla/layout/html/forms/src/nsComboboxControlFrame.cpp
index 388a11be86d..68eef45f445 100644
--- a/mozilla/layout/html/forms/src/nsComboboxControlFrame.cpp
+++ b/mozilla/layout/html/forms/src/nsComboboxControlFrame.cpp
@@ -867,7 +867,7 @@ nsComboboxControlFrame::ReflowItems(nsIPresContext* aPresContext,
       if (optionElement) {
         nsAutoString text;
         rv = optionElement->GetLabel(text);
-        if (NS_CONTENT_ATTR_HAS_VALUE != rv || 0 == text.Length()) {
+        if (NS_CONTENT_ATTR_HAS_VALUE != rv || text.IsEmpty()) {
           if (NS_OK == optionElement->GetText(text)) {
             nscoord width;
             aReflowState.rendContext->GetWidth(text, width);
@@ -1928,7 +1928,7 @@ nsComboboxControlFrame::RedisplayText(PRInt32 aIndex)
       fragment->AppendTo(value);
     }
     PRBool shouldSetValue = PR_FALSE;
-    if (NS_FAILED(result) || value.Length() == 0) {
+    if (NS_FAILED(result) || value.IsEmpty()) {
       shouldSetValue = PR_TRUE;
     } else {
        shouldSetValue = value != textToDisplay;
diff --git a/mozilla/layout/html/forms/src/nsGfxCheckboxControlFrame.cpp b/mozilla/layout/html/forms/src/nsGfxCheckboxControlFrame.cpp
index 0ed1d5be794..dba59377cd3 100644
--- a/mozilla/layout/html/forms/src/nsGfxCheckboxControlFrame.cpp
+++ b/mozilla/layout/html/forms/src/nsGfxCheckboxControlFrame.cpp
@@ -231,7 +231,7 @@ nsGfxCheckboxControlFrame::Paint(nsIPresContext*   aPresContext,
     if (!mCheckButtonFaceStyle && GetCheckboxState()) {
       const nsStyleBackground* myColor = mCheckButtonFaceStyle->GetStyleBackground();
 
-      if (myColor->mBackgroundImage.Length() > 0) {
+      if (!myColor->mBackgroundImage.IsEmpty()) {
         const nsStyleBorder* myBorder = mCheckButtonFaceStyle->GetStyleBorder();
         const nsStylePadding* myPadding = mCheckButtonFaceStyle->GetStylePadding();
         const nsStylePosition* myPosition = mCheckButtonFaceStyle->GetStylePosition();
diff --git a/mozilla/layout/html/forms/src/nsIsIndexFrame.cpp b/mozilla/layout/html/forms/src/nsIsIndexFrame.cpp
index 060acd9cef9..83d96e8ff0a 100644
--- a/mozilla/layout/html/forms/src/nsIsIndexFrame.cpp
+++ b/mozilla/layout/html/forms/src/nsIsIndexFrame.cpp
@@ -156,7 +156,7 @@ nsIsIndexFrame::UpdatePromptLabel()
       }
     }
   }
-  if (prompt.Length() == 0) {
+  if (prompt.IsEmpty()) {
     // Generate localized label.
     // We can't make any assumption as to what the default would be
     // because the value is localized for non-english platforms, thus
diff --git a/mozilla/layout/html/forms/src/nsListControlFrame.cpp b/mozilla/layout/html/forms/src/nsListControlFrame.cpp
index 27a37283a9d..17edecd6876 100644
--- a/mozilla/layout/html/forms/src/nsListControlFrame.cpp
+++ b/mozilla/layout/html/forms/src/nsListControlFrame.cpp
@@ -2194,15 +2194,15 @@ nsListControlFrame::GetOptionText(PRInt32 aIndex, nsAString & aStr)
         rv = optionElement->GetLabel(text);
         // the return value is always NS_OK from DOMElements
         // it is meaningless to check for it
-        if (text.Length() > 0) { 
+        if (!text.IsEmpty()) { 
           nsAutoString compressText = text;
           compressText.CompressWhitespace(PR_TRUE, PR_TRUE);
-          if (compressText.Length() != 0) {
+          if (!compressText.IsEmpty()) {
             text = compressText;
           }
         }
 
-        if (0 == text.Length()) {
+        if (text.IsEmpty()) {
           // the return value is always NS_OK from DOMElements
           // it is meaningless to check for it
           optionElement->GetText(text);
diff --git a/mozilla/layout/mathml/base/src/nsMathMLmactionFrame.cpp b/mozilla/layout/mathml/base/src/nsMathMLmactionFrame.cpp
index 039c2521499..89469dea942 100644
--- a/mozilla/layout/mathml/base/src/nsMathMLmactionFrame.cpp
+++ b/mozilla/layout/mathml/base/src/nsMathMLmactionFrame.cpp
@@ -426,7 +426,7 @@ nsMathMLmactionFrame::MouseClick(nsIDOMEvent* aMouseEvent)
     }
   }
   else if (NS_MATHML_ACTION_TYPE_RESTYLE == mActionType) {
-    if (0 < mRestyle.Length()) {
+    if (!mRestyle.IsEmpty()) {
       nsCOMPtr<nsIDOMElement> node( do_QueryInterface(mContent) );
       if (node.get()) {
         if (NS_CONTENT_ATTR_HAS_VALUE == mContent->GetAttr(kNameSpaceID_None, 
diff --git a/mozilla/layout/mathml/base/src/nsMathMLmfencedFrame.cpp b/mozilla/layout/mathml/base/src/nsMathMLmfencedFrame.cpp
index 32c1b79240b..abce31a1d01 100644
--- a/mozilla/layout/mathml/base/src/nsMathMLmfencedFrame.cpp
+++ b/mozilla/layout/mathml/base/src/nsMathMLmfencedFrame.cpp
@@ -147,7 +147,7 @@ nsMathMLmfencedFrame::CreateFencesAndSeparators(nsIPresContext* aPresContext)
   else
     data.Truncate();
 
-  if (0 < data.Length()) {
+  if (!data.IsEmpty()) {
     mOpenChar = new nsMathMLChar;
     if (!mOpenChar) return NS_ERROR_OUT_OF_MEMORY;
     mOpenChar->SetData(aPresContext, data);
@@ -168,7 +168,7 @@ nsMathMLmfencedFrame::CreateFencesAndSeparators(nsIPresContext* aPresContext)
   else
     data.Truncate();
 
-  if (0 < data.Length()) {
+  if (!data.IsEmpty()) {
     mCloseChar = new nsMathMLChar;
     if (!mCloseChar) return NS_ERROR_OUT_OF_MEMORY;
     mCloseChar->SetData(aPresContext, data);
diff --git a/mozilla/layout/mathml/base/src/nsMathMLmfracFrame.cpp b/mozilla/layout/mathml/base/src/nsMathMLmfracFrame.cpp
index 421c19ac56f..0a1c235cb80 100644
--- a/mozilla/layout/mathml/base/src/nsMathMLmfracFrame.cpp
+++ b/mozilla/layout/mathml/base/src/nsMathMLmfracFrame.cpp
@@ -161,7 +161,7 @@ nsMathMLmfracFrame::CalcLineThickness(nsIPresContext*  aPresContext,
   nscoord lineThickness = aDefaultRuleThickness;
   nscoord minimumThickness = onePixel;
 
-  if (0 < aThicknessAttribute.Length()) {
+  if (!aThicknessAttribute.IsEmpty()) {
     if (aThicknessAttribute.Equals(NS_LITERAL_STRING("thin"))) {
       lineThickness = NSToCoordFloor(defaultThickness * THIN_FRACTION_LINE);
       minimumThickness = onePixel * THIN_FRACTION_LINE_MINIMUM_PIXELS;
diff --git a/mozilla/layout/svg/base/src/nsSVGStroke.cpp b/mozilla/layout/svg/base/src/nsSVGStroke.cpp
index 924e39059da..37558e3b4fb 100644
--- a/mozilla/layout/svg/base/src/nsSVGStroke.cpp
+++ b/mozilla/layout/svg/base/src/nsSVGStroke.cpp
@@ -82,7 +82,7 @@ nsSVGStroke::Build(ArtVpath* path, const nsSVGStrokeStyle& style)
       NS_ERROR("not reached");
   }
 
-  if (style.dasharray.Length() > 0) {
+  if (!style.dasharray.IsEmpty()) {
     ArtVpathDash dash;
     dash.offset = style.dashoffset;
 
diff --git a/mozilla/layout/xul/base/src/nsImageBoxFrame.cpp b/mozilla/layout/xul/base/src/nsImageBoxFrame.cpp
index d75c1d21772..82f520813ee 100644
--- a/mozilla/layout/xul/base/src/nsImageBoxFrame.cpp
+++ b/mozilla/layout/xul/base/src/nsImageBoxFrame.cpp
@@ -376,7 +376,7 @@ nsImageBoxFrame::GetImageSource()
     // get the list-style-image
     const nsStyleList* myList = GetStyleList();
   
-    if (myList->mListStyleImage.Length() > 0) {
+    if (!myList->mListStyleImage.IsEmpty()) {
       mSrc = myList->mListStyleImage;
     }
   }
diff --git a/mozilla/layout/xul/base/src/nsStackFrame.cpp b/mozilla/layout/xul/base/src/nsStackFrame.cpp
index eb5758bdb21..1ba23efd875 100644
--- a/mozilla/layout/xul/base/src/nsStackFrame.cpp
+++ b/mozilla/layout/xul/base/src/nsStackFrame.cpp
@@ -141,7 +141,7 @@ nsStackFrame::GetFrameForPoint(nsIPresContext* aPresContext,
       PRBool        transparentBG = NS_STYLE_BG_COLOR_TRANSPARENT ==
                                     (color->mBackgroundFlags & NS_STYLE_BG_COLOR_TRANSPARENT);
 
-      PRBool backgroundImage = (color->mBackgroundImage.Length() > 0);
+      PRBool backgroundImage = !color->mBackgroundImage.IsEmpty();
 
       if (!transparentBG || backgroundImage)
       {
diff --git a/mozilla/layout/xul/base/src/nsTextBoxFrame.cpp b/mozilla/layout/xul/base/src/nsTextBoxFrame.cpp
index a8f7f97ea43..bb6bfb38b2a 100644
--- a/mozilla/layout/xul/base/src/nsTextBoxFrame.cpp
+++ b/mozilla/layout/xul/base/src/nsTextBoxFrame.cpp
@@ -317,7 +317,7 @@ nsTextBoxFrame::PaintTitle(nsIPresContext*      aPresContext,
                            const nsRect&        aDirtyRect,
                            const nsRect&        aRect)
 {
-    if (mTitle.Length() == 0)
+    if (mTitle.IsEmpty())
         return NS_OK;
 
     // determine (cropped) title and underline position
@@ -509,7 +509,7 @@ nsTextBoxFrame::CalculateTitleForWidth(nsIPresContext*      aPresContext,
                                        nsIRenderingContext& aRenderingContext,
                                        nscoord              aWidth)
 {
-    if (mTitle.Length() == 0)
+    if (mTitle.IsEmpty())
         return;
 
     nsCOMPtr<nsIDeviceContext> deviceContext;
diff --git a/mozilla/layout/xul/base/src/tree/src/nsTreeBodyFrame.cpp b/mozilla/layout/xul/base/src/tree/src/nsTreeBodyFrame.cpp
index 8c1106b5245..59e451bc3e3 100644
--- a/mozilla/layout/xul/base/src/tree/src/nsTreeBodyFrame.cpp
+++ b/mozilla/layout/xul/base/src/tree/src/nsTreeBodyFrame.cpp
@@ -846,7 +846,7 @@ NS_IMETHODIMP nsTreeBodyFrame::GetKeyColumnIndex(PRInt32 *_retval)
       first = currCol->GetColIndex();
     
     currCol->GetElement()->GetAttr(kNameSpaceID_None, nsXULAtoms::sortDirection, attr);
-    if (attr.Length() > 0) { // Use sorted column as the primary
+    if (!attr.IsEmpty()) { // Use sorted column as the primary
       sorted = currCol->GetColIndex();
       break;
     }
@@ -1904,7 +1904,7 @@ nsTreeBodyFrame::GetImage(PRInt32 aRowIndex, const PRUnichar* aColID, PRBool aUs
   const nsAString* imagePtr;
   nsAutoString imageSrc;
   mView->GetImageSrc(aRowIndex, aColID, imageSrc);
-  if (!aUseContext && imageSrc.Length() > 0) {
+  if (!aUseContext && !imageSrc.IsEmpty()) {
     imagePtr = &imageSrc;
     aAllowImageRegions = PR_FALSE;
   }
@@ -1912,7 +1912,7 @@ nsTreeBodyFrame::GetImage(PRInt32 aRowIndex, const PRUnichar* aColID, PRBool aUs
     // Obtain the URL from the style context.
     aAllowImageRegions = PR_TRUE;
     const nsStyleList* myList = aStyleContext->GetStyleList();
-    if (myList->mListStyleImage.Length() > 0)
+    if (!myList->mListStyleImage.IsEmpty())
       imagePtr = &myList->mListStyleImage;
     else
       return NS_OK;
diff --git a/mozilla/mailnews/addrbook/src/nsAbOutlookCard.cpp b/mozilla/mailnews/addrbook/src/nsAbOutlookCard.cpp
index c804692e282..69d69e6205f 100644
--- a/mozilla/mailnews/addrbook/src/nsAbOutlookCard.cpp
+++ b/mozilla/mailnews/addrbook/src/nsAbOutlookCard.cpp
@@ -330,7 +330,7 @@ NS_IMETHODIMP nsAbOutlookCard::EditCardToDatabase(const char *aUru)
     GetHomeAddress(getter_Copies(unichar)) ;
     GetHomeAddress2(getter_Copies(unichar2)) ;
     utility.Assign(unichar.get()) ;
-    if (utility.Length() > 0) { utility.AppendWithConversion(CRLF) ; }
+    if (!utility.IsEmpty()) { utility.AppendWithConversion(CRLF) ; }
     utility.Append(unichar2.get()) ;
     if (!mapiAddBook->SetPropertyUString(*mMapiData, PR_HOME_ADDRESS_STREET_W, utility.get())) {
         PRINTF(("Cannot set home address.\n")) ;
@@ -338,7 +338,7 @@ NS_IMETHODIMP nsAbOutlookCard::EditCardToDatabase(const char *aUru)
     GetWorkAddress(getter_Copies(unichar)) ;
     GetWorkAddress2(getter_Copies(unichar2)) ;
     utility.Assign(unichar.get()) ;
-    if (utility.Length() > 0) { utility.AppendWithConversion(CRLF) ; }
+    if (!utility.IsEmpty()) { utility.AppendWithConversion(CRLF) ; }
     utility.Append(unichar2.get()) ;
     if (!mapiAddBook->SetPropertyUString(*mMapiData, PR_BUSINESS_ADDRESS_STREET_W, utility.get())) {
         PRINTF(("Cannot set work address.\n")) ;
diff --git a/mozilla/mailnews/addrbook/src/nsAbOutlookDirectory.cpp b/mozilla/mailnews/addrbook/src/nsAbOutlookDirectory.cpp
index 0bd17362cef..696d1183ed4 100644
--- a/mozilla/mailnews/addrbook/src/nsAbOutlookDirectory.cpp
+++ b/mozilla/mailnews/addrbook/src/nsAbOutlookDirectory.cpp
@@ -309,7 +309,7 @@ NS_IMETHODIMP nsAbOutlookDirectory::DeleteCards(nsISupportsArray *aCardList)
         NS_ENSURE_SUCCESS(retCode, retCode) ;
 
         retCode = ExtractCardEntry(card, entryString) ;
-        if (NS_SUCCEEDED(retCode) && entryString.Length() > 0) {
+        if (NS_SUCCEEDED(retCode) && !entryString.IsEmpty()) {
 
             cardEntry.Assign(entryString) ;
             if (!mapiAddBook->DeleteEntry(*mMapiData, cardEntry)) {
@@ -347,7 +347,7 @@ NS_IMETHODIMP nsAbOutlookDirectory::DeleteDirectory(nsIAbDirectory *aDirectory)
 
     if (!mapiAddBook->IsOK()) { return NS_ERROR_FAILURE ; }
     retCode = ExtractDirectoryEntry(aDirectory, entryString) ;
-    if (NS_SUCCEEDED(retCode) && entryString.Length() > 0) {
+    if (NS_SUCCEEDED(retCode) && !entryString.IsEmpty()) {
         nsMapiEntry directoryEntry ;
 
         directoryEntry.Assign(entryString) ;
@@ -412,7 +412,7 @@ NS_IMETHODIMP nsAbOutlookDirectory::AddMailList(nsIAbDirectory *aMailList)
 
     if (!mapiAddBook->IsOK()) { return NS_ERROR_FAILURE ; }
     retCode = ExtractDirectoryEntry(aMailList, entryString) ;
-    if (NS_SUCCEEDED(retCode) && entryString.Length() > 0) {
+    if (NS_SUCCEEDED(retCode) && !entryString.IsEmpty()) {
         nsMapiEntry sourceEntry ;
 
         sourceEntry.Assign(entryString) ;
@@ -1256,7 +1256,7 @@ nsresult nsAbOutlookDirectory::CreateCard(nsIAbCard *aData, nsIAbCard **aNewCard
     // If we get a RDF resource and it maps onto an Outlook card uri,
     // we simply copy the contents of the Outlook card.
     retCode = ExtractCardEntry(aData, entryString) ;
-    if (NS_SUCCEEDED(retCode) && entryString.Length() > 0) {
+    if (NS_SUCCEEDED(retCode) && !entryString.IsEmpty()) {
         nsMapiEntry sourceEntry ;
         
         
diff --git a/mozilla/mailnews/addrbook/src/nsAddrDatabase.cpp b/mozilla/mailnews/addrbook/src/nsAddrDatabase.cpp
index 8b2c68d875e..1c3c7613268 100644
--- a/mozilla/mailnews/addrbook/src/nsAddrDatabase.cpp
+++ b/mozilla/mailnews/addrbook/src/nsAddrDatabase.cpp
@@ -2619,61 +2619,61 @@ nsresult nsAddrDatabase::GetCardFromDB(nsIAbCard *newCard, nsIMdbRow* cardRow)
   // there is no reason to set / copy all these attributes on the card, when we'll never even
   // ask for them.
     err = GetStringColumn(cardRow, m_FirstNameColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetFirstName(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_LastNameColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetLastName(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_PhoneticFirstNameColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetPhoneticFirstName(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_PhoneticLastNameColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetPhoneticLastName(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_DisplayNameColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetDisplayName(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_NickNameColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetNickName(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_PriEmailColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetPrimaryEmail(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_2ndEmailColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetSecondEmail(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_DefaultEmailColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetDefaultEmail(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_CardTypeColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetCardType(tempString.get());
     }
@@ -2684,234 +2684,234 @@ nsresult nsAddrDatabase::GetCardFromDB(nsIAbCard *newCard, nsIMdbRow* cardRow)
         newCard->SetPreferMailFormat(format);
 
     err = GetStringColumn(cardRow, m_WorkPhoneColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetWorkPhone(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_HomePhoneColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetHomePhone(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_FaxColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetFaxNumber(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_PagerColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetPagerNumber(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_CellularColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetCellularNumber(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_WorkPhoneTypeColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
         newCard->SetWorkPhoneType(tempString.get());
 
     err = GetStringColumn(cardRow, m_HomePhoneTypeColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
         newCard->SetHomePhoneType(tempString.get());
 
     err = GetStringColumn(cardRow, m_FaxTypeColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
         newCard->SetFaxNumberType(tempString.get());
 
     err = GetStringColumn(cardRow, m_PagerTypeColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
         newCard->SetPagerNumberType(tempString.get());
 
     err = GetStringColumn(cardRow, m_CellularTypeColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
         newCard->SetCellularNumberType(tempString.get());
 
     err = GetStringColumn(cardRow, m_HomeAddressColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetHomeAddress(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_HomeAddress2ColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetHomeAddress2(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_HomeCityColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetHomeCity(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_HomeStateColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetHomeState(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_HomeZipCodeColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetHomeZipCode(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_HomeCountryColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetHomeCountry(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_WorkAddressColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetWorkAddress(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_WorkAddress2ColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetWorkAddress2(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_WorkCityColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetWorkCity(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_WorkStateColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetWorkState(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_WorkZipCodeColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetWorkZipCode(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_WorkCountryColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetWorkCountry(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_JobTitleColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetJobTitle(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_DepartmentColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetDepartment(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_CompanyColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetCompany(tempString.get());
     }
 
     // AimScreenName
     err = GetStringColumn(cardRow, m_AimScreenNameColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
         newCard->SetAimScreenName(tempString.get());
 
     err = GetStringColumn(cardRow, m_AnniversaryYearColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
         newCard->SetAnniversaryYear(tempString.get());
 
     err = GetStringColumn(cardRow, m_AnniversaryMonthColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
         newCard->SetAnniversaryMonth(tempString.get());
 
     err = GetStringColumn(cardRow, m_AnniversaryDayColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
         newCard->SetAnniversaryDay(tempString.get());
 
     err = GetStringColumn(cardRow, m_SpouseNameColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
         newCard->SetSpouseName(tempString.get());
 
     err = GetStringColumn(cardRow, m_FamilyNameColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
         newCard->SetFamilyName(tempString.get());
 
     err = GetStringColumn(cardRow, m_DefaultAddressColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
         newCard->SetDefaultAddress(tempString.get());
 
     err = GetStringColumn(cardRow, m_CategoryColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
         newCard->SetCategory(tempString.get());
 
     err = GetStringColumn(cardRow, m_WebPage1ColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetWebPage1(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_WebPage2ColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetWebPage2(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_BirthYearColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetBirthYear(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_BirthMonthColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetBirthMonth(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_BirthDayColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetBirthDay(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_Custom1ColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetCustom1(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_Custom2ColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetCustom2(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_Custom3ColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetCustom3(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_Custom4ColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetCustom4(tempString.get());
     }
 
     err = GetStringColumn(cardRow, m_NotesColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newCard->SetNotes(tempString.get());
     }
@@ -2941,18 +2941,18 @@ nsresult nsAddrDatabase::GetListCardFromDB(nsIAbCard *listCard, nsIMdbRow* listR
     nsAutoString tempString;
 
     err = GetStringColumn(listRow, m_ListNameColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         listCard->SetDisplayName(tempString.get());
         listCard->SetLastName(tempString.get());
     }
     err = GetStringColumn(listRow, m_ListNickNameColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         listCard->SetNickName(tempString.get());
     }
     err = GetStringColumn(listRow, m_ListDescriptionColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         listCard->SetNotes(tempString.get());
     }
@@ -2976,17 +2976,17 @@ nsresult nsAddrDatabase::GetListFromDB(nsIAbDirectory *newList, nsIMdbRow* listR
     nsAutoString tempString;
 
     err = GetStringColumn(listRow, m_ListNameColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newList->SetDirName(tempString.get());
     }
     err = GetStringColumn(listRow, m_ListNickNameColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newList->SetListNickName(tempString.get());
     }
     err = GetStringColumn(listRow, m_ListDescriptionColumnToken, tempString);
-    if (NS_SUCCEEDED(err) && tempString.Length())
+    if (NS_SUCCEEDED(err) && !tempString.IsEmpty())
     {
         newList->SetDescription(tempString.get());
     }
diff --git a/mozilla/mailnews/addrbook/src/nsAddressBook.cpp b/mozilla/mailnews/addrbook/src/nsAddressBook.cpp
index e020cb274d2..69dd25428ce 100644
--- a/mozilla/mailnews/addrbook/src/nsAddressBook.cpp
+++ b/mozilla/mailnews/addrbook/src/nsAddressBook.cpp
@@ -734,8 +734,8 @@ nsresult AddressBookParser::ParseLDIFFile()
         }
     }
     //last row
-    if (mLine.Length() > 0 && mLine.Find("groupOfNames") == kNotFound)
-        AddLdifRowToDatabase(PR_FALSE); 
+    if (!mLine.IsEmpty() && mLine.Find("groupOfNames") == kNotFound)
+        AddLdifRowToDatabase(PR_FALSE);
 
     // mail Lists
     PRInt32 i, pos, size;
@@ -824,7 +824,7 @@ void AddressBookParser::AddLdifRowToDatabase(PRBool bIsList)
 
 void AddressBookParser::ClearLdifRecordBuffer()
 {
-  if (mLine.Length() > 0)
+  if (!mLine.IsEmpty())
   {
       mLine.Truncate();
       mLFCount = 0;
diff --git a/mozilla/mailnews/base/search/src/nsMsgFilterList.cpp b/mozilla/mailnews/base/search/src/nsMsgFilterList.cpp
index d38730a1502..55ce1552d32 100644
--- a/mozilla/mailnews/base/search/src/nsMsgFilterList.cpp
+++ b/mozilla/mailnews/base/search/src/nsMsgFilterList.cpp
@@ -1079,7 +1079,7 @@ NS_IMETHODIMP nsMsgFilterList::GetShouldDownloadAllHeaders(PRBool *aResult)
 nsresult nsMsgFilterList::ComputeArbitraryHeaders()
 {
   nsresult rv = NS_OK;
-  if (m_arbitraryHeaders.Length() == 0)
+  if (m_arbitraryHeaders.IsEmpty())
   {
     PRUint32 numFilters;
     rv = m_filters->Count(&numFilters);
@@ -1102,7 +1102,7 @@ nsresult nsMsgFilterList::ComputeArbitraryHeaders()
           filter->GetTerm(i, &attrib, nsnull,nsnull,nsnull, getter_Copies(arbitraryHeader));
           if (arbitraryHeader && arbitraryHeader[0])
           {
-            if (m_arbitraryHeaders.Length() == 0)
+            if (m_arbitraryHeaders.IsEmpty())
               m_arbitraryHeaders.Assign(arbitraryHeader);
             else if (PL_strncasecmp(m_arbitraryHeaders.get(), arbitraryHeader, arbitraryHeader.Length()))
             {
diff --git a/mozilla/mailnews/base/search/src/nsMsgSearchTerm.cpp b/mozilla/mailnews/base/search/src/nsMsgSearchTerm.cpp
index d0fd4be82d3..b3b85b539a9 100644
--- a/mozilla/mailnews/base/search/src/nsMsgSearchTerm.cpp
+++ b/mozilla/mailnews/base/search/src/nsMsgSearchTerm.cpp
@@ -821,7 +821,7 @@ nsresult nsMsgSearchTerm::MatchBody (nsIMsgSearchScopeTerm *scope, PRUint32 offs
 					StripQuotedPrintable ((unsigned char*)buf);
 			    nsCString  compare(buf);
 //				ConvertToUnicode(charset, buf, compare);
-				if (compare.Length() > 0) {
+				if (!compare.IsEmpty()) {
 					char startChar = (char) compare.CharAt(0);
 					if (startChar != nsCRT::CR && startChar != nsCRT::LF)
 					{
diff --git a/mozilla/mailnews/base/src/nsMsgAccountManager.cpp b/mozilla/mailnews/base/src/nsMsgAccountManager.cpp
index 74b01c5ef82..76d678adc45 100644
--- a/mozilla/mailnews/base/src/nsMsgAccountManager.cpp
+++ b/mozilla/mailnews/base/src/nsMsgAccountManager.cpp
@@ -1370,8 +1370,8 @@ nsMsgAccountManager::LoadAccounts()
                                           getter_Copies(appendAccountList));
 
       // If there are pre-configured accounts, we need to add them to the existing list.
-      if (appendAccountList.Length() > 0) {
-        if (accountList.Length() > 0) {
+      if (!appendAccountList.IsEmpty()) {
+        if (!accountList.IsEmpty()) {
           nsCStringArray existingAccountsArray;
           existingAccountsArray.ParseString(accountList.get(), ACCOUNT_DELIMITER);
 
diff --git a/mozilla/mailnews/base/util/nsMsgI18N.cpp b/mozilla/mailnews/base/util/nsMsgI18N.cpp
index 98739ee72ad..6d95bf19efd 100644
--- a/mozilla/mailnews/base/util/nsMsgI18N.cpp
+++ b/mozilla/mailnews/base/util/nsMsgI18N.cpp
@@ -102,7 +102,7 @@ nsresult nsMsgI18NConvertFromUnicode(const nsCString& aCharset,
   nsCOMPtr <nsICharsetAlias> calias = do_GetService(NS_CHARSETALIAS_CONTRACTID, &res);
   if (NS_SUCCEEDED(res)) {
     nsAutoString aAlias; aAlias.AssignWithConversion(aCharset.get());
-    if (aAlias.Length()) {
+    if (!aAlias.IsEmpty()) {
       res = calias->GetPreferred(aAlias, convCharset);
     }
   }
@@ -170,7 +170,7 @@ nsresult nsMsgI18NConvertToUnicode(const nsCString& aCharset,
   nsCOMPtr <nsICharsetAlias> calias = do_GetService(NS_CHARSETALIAS_CONTRACTID, &res);
   if (NS_SUCCEEDED(res)) {
     nsAutoString aAlias; aAlias.AssignWithConversion(aCharset.get());
-    if (aAlias.Length()) {
+    if (!aAlias.IsEmpty()) {
       res = calias->GetPreferred(aAlias, convCharset);
     }
   }
@@ -365,7 +365,7 @@ const char * nsMsgI18NFileSystemCharset()
 	/* Get a charset used for the file. */
 	static nsCAutoString fileSystemCharset;
 
-	if (fileSystemCharset.Length() < 1) 
+	if (fileSystemCharset.IsEmpty()) 
 	{
 		nsresult rv;
 		nsCOMPtr <nsIPlatformCharset> platformCharset = do_GetService(NS_PLATFORMCHARSET_CONTRACTID, &rv);
diff --git a/mozilla/mailnews/base/util/nsMsgUtils.cpp b/mozilla/mailnews/base/util/nsMsgUtils.cpp
index 22def72995b..ad23c8525ef 100644
--- a/mozilla/mailnews/base/util/nsMsgUtils.cpp
+++ b/mozilla/mailnews/base/util/nsMsgUtils.cpp
@@ -316,12 +316,11 @@ nsresult NS_MsgCreatePathStringFromFolderURI(const char *folderURI, nsCString& p
     while (startSlashPos != -1) {
 	  oldPath.Mid(pathPiece, startSlashPos + 1, endSlashPos - startSlashPos);
       // skip leading '/' (and other // style things)
-      if (pathPiece.Length() > 0) {
+      if (!pathPiece.IsEmpty()) {
 
         // add .sbd onto the previous path
         if (haveFirst) {
-          pathString+=".sbd";
-          pathString += "/";
+          pathString += ".sbd/";
         }
         
         NS_MsgHashIfNecessary(pathPiece);
diff --git a/mozilla/mailnews/compose/src/nsSmtpService.cpp b/mozilla/mailnews/compose/src/nsSmtpService.cpp
index a8e95402bd9..6d7fe24820e 100644
--- a/mozilla/mailnews/compose/src/nsSmtpService.cpp
+++ b/mozilla/mailnews/compose/src/nsSmtpService.cpp
@@ -473,7 +473,7 @@ nsSmtpService::loadSmtpServers()
     // Get the list of smtp servers (either from regular pref i.e, mail.smtpservers or
     // from preconfigured pref mail.smtpservers.appendsmtpservers) and create a keyed 
     // server list.
-    if ((serverList.Length() > 0) || (appendServerList.Length() > 0)) {
+    if (!serverList.IsEmpty() || !appendServerList.IsEmpty()) {
       /** 
        * Check to see if we need to add pre-configured smtp servers.
        * Following prefs are important to note in understanding the procedure here.
@@ -508,8 +508,8 @@ nsSmtpService::loadSmtpServers()
       // Update the smtp server list if needed
       if ((appendSmtpServersCurrentVersion <= appendSmtpServersDefaultVersion)) {
         // If there are pre-configured servers, add them to the existing server list
-        if (appendServerList.Length() > 0) {
-          if (serverList.Length() > 0) {
+        if (!appendServerList.IsEmpty()) {
+          if (!serverList.IsEmpty()) {
             nsCStringArray existingSmtpServersArray;
             existingSmtpServersArray.ParseString(serverList.get(), SERVER_DELIMITER);
 
diff --git a/mozilla/mailnews/db/msgdb/src/nsMsgDatabase.cpp b/mozilla/mailnews/db/msgdb/src/nsMsgDatabase.cpp
index b7b5591da97..de34d0b343c 100644
--- a/mozilla/mailnews/db/msgdb/src/nsMsgDatabase.cpp
+++ b/mozilla/mailnews/db/msgdb/src/nsMsgDatabase.cpp
@@ -3488,7 +3488,7 @@ nsresult nsMsgDatabase::ThreadNewHdr(nsMsgHdr* newHdr, PRBool &newThread)
 		// but we have to handle case of promoting new header to top-level
 		// in case the top-level header comes after a reply.
 
-		if (reference.Length() == 0)
+		if (reference.IsEmpty())
 			break;
 
 		thread = getter_AddRefs(GetThreadForReference(reference, getter_AddRefs(replyToHdr))) ;
diff --git a/mozilla/mailnews/db/msgdb/src/nsMsgOfflineImapOperation.cpp b/mozilla/mailnews/db/msgdb/src/nsMsgOfflineImapOperation.cpp
index 425d102a54c..eeae0ed071e 100644
--- a/mozilla/mailnews/db/msgdb/src/nsMsgOfflineImapOperation.cpp
+++ b/mozilla/mailnews/db/msgdb/src/nsMsgOfflineImapOperation.cpp
@@ -210,7 +210,7 @@ nsresult nsMsgOfflineImapOperation::GetCopiesFromDB()
   nsresult rv = m_mdb->GetProperty(m_mdbRow, PROP_COPY_DESTS, getter_Copies(copyDests));
   nsCAutoString copyDestsCString((const char *) copyDests);
   // use 0x1 as the delimiter between folder names since it's not a legal character
-  if (NS_SUCCEEDED(rv) && copyDestsCString.Length() > 0)
+  if (NS_SUCCEEDED(rv) && !copyDestsCString.IsEmpty())
   {
     PRInt32 curCopyDestStart = 0;
     PRInt32 nextCopyDestPos = 0;
diff --git a/mozilla/mailnews/imap/src/nsImapMailFolder.cpp b/mozilla/mailnews/imap/src/nsImapMailFolder.cpp
index bd36d1bd1c3..635103179ea 100644
--- a/mozilla/mailnews/imap/src/nsImapMailFolder.cpp
+++ b/mozilla/mailnews/imap/src/nsImapMailFolder.cpp
@@ -527,7 +527,7 @@ nsresult nsImapMailFolder::CreateSubFolders(nsFileSpec &path)
     {
       // use the unicode name as the "pretty" name. Set it so it won't be
       // automatically computed from the URI, which is in utf7 form.
-      if (currentFolderNameStr.Length() > 0)
+      if (!currentFolderNameStr.IsEmpty())
         child->SetPrettyName(currentFolderNameStr.get());
 
     }
@@ -876,7 +876,7 @@ NS_IMETHODIMP nsImapMailFolder::CreateClientSubfolderInfo(const char *folderName
       if (imapFolder)
       {
         nsCAutoString onlineName(m_onlineFolderName); 
-        if (onlineName.Length() > 0)
+        if (!onlineName.IsEmpty())
           onlineName.Append(char(hierarchyDelimiter));
         onlineName.AppendWithConversion(folderNameStr);
         imapFolder->SetVerifiedAsOnlineFolder(PR_TRUE);
@@ -1798,7 +1798,7 @@ nsImapMailFolder::GetDBFolderInfoAndDB(nsIDBFolderInfo **folderInfo, nsIMsgDatab
           nsAutoString autoOnlineName; 
           // autoOnlineName.AssignWithConversion(name);
           (*folderInfo)->GetMailboxName(&autoOnlineName);
-          if (autoOnlineName.Length() == 0)
+          if (autoOnlineName.IsEmpty())
           {
             nsXPIDLCString uri;
             rv = GetURI(getter_Copies(uri));
@@ -3127,13 +3127,13 @@ nsresult nsImapMailFolder::GetFolderOwnerUserName(char **userName)
   if (!(mFlags & MSG_FOLDER_FLAG_IMAP_OTHER_USER))
     return NS_OK;
   
-  if (!m_ownerUserName.Length())
+  if (m_ownerUserName.IsEmpty())
   {
     nsXPIDLCString onlineName;
     GetOnlineName(getter_Copies(onlineName));
     m_ownerUserName = nsIMAPNamespaceList::GetFolderOwnerNameFromPath(GetNamespaceForFolder(), onlineName.get());
   }
-  *userName = (m_ownerUserName.Length()) ? ToNewCString(m_ownerUserName) : nsnull;
+  *userName = !m_ownerUserName.IsEmpty() ? ToNewCString(m_ownerUserName) : nsnull;
   return NS_OK;
 }
 
@@ -3148,7 +3148,7 @@ nsresult nsImapMailFolder::GetOwnersOnlineFolderName(char **retName)
   {
     nsXPIDLCString user;
     GetFolderOwnerUserName(getter_Copies(user));
-    if (onlineName.Length() && user.Length())
+    if (!onlineName.IsEmpty() && !user.IsEmpty())
     {
       const char *where = PL_strstr(onlineName.get(), user.get());
       NS_ASSERTION(where, "user name not in online name");
@@ -3264,7 +3264,7 @@ NS_IMETHODIMP nsImapMailFolder::GetHasAdminUrl(PRBool *aBool)
   NS_ENSURE_ARG_POINTER(aBool);
   nsXPIDLCString manageMailAccountUrl;
   nsresult rv = GetServerAdminUrl(getter_Copies(manageMailAccountUrl));
-  *aBool = (NS_SUCCEEDED(rv) && manageMailAccountUrl.Length());
+  *aBool = (NS_SUCCEEDED(rv) && !manageMailAccountUrl.IsEmpty());
   return rv;
 }
 
@@ -3644,7 +3644,7 @@ NS_IMETHODIMP nsImapMailFolder::DownloadMessagesForOffline(nsISupportsArray *mes
 //  return DownloadAllForOffline(nsnull, window);
 #endif
   nsresult rv = BuildIdsAndKeyArray(messages, messageIds, srcKeyArray);
-  if (NS_FAILED(rv) || messageIds.Length() == 0) return rv;
+  if (NS_FAILED(rv) || messageIds.IsEmpty()) return rv;
 
   nsCOMPtr<nsIImapService> imapService = do_GetService(NS_IMAPSERVICE_CONTRACTID, &rv);
   NS_ENSURE_SUCCESS(rv,rv);
@@ -5030,7 +5030,7 @@ nsImapMailFolder::FillInFolderProps(nsIMsgImapFolderProps *aFolderProps)
     nsXPIDLCString owner;
     nsXPIDLString uniOwner;
     GetFolderOwnerUserName(getter_Copies(owner));
-    if (!owner.Length())
+    if (owner.IsEmpty())
     {
       rv = IMAPGetStringByID(folderTypeStringID, getter_Copies(uniOwner));
       // Another user's folder, for which we couldn't find an owner name
@@ -5060,9 +5060,9 @@ nsImapMailFolder::FillInFolderProps(nsIMsgImapFolderProps *aFolderProps)
   if (NS_SUCCEEDED(rv))
     aFolderProps->SetFolderType(folderType);
 
-  if (!folderTypeDesc.Length() && folderTypeDescStringID != 0)
+  if (folderTypeDesc.IsEmpty() && folderTypeDescStringID != 0)
     rv = IMAPGetStringByID(folderTypeDescStringID, getter_Copies(folderTypeDesc));
-  if (folderTypeDesc.Length())
+  if (!folderTypeDesc.IsEmpty())
     aFolderProps->SetFolderTypeDescription(folderTypeDesc.get());
 
   nsXPIDLString rightsString;
@@ -5167,7 +5167,7 @@ void nsMsgIMAPFolderACL::BuildInitialACLFromCache()
   if (startingFlags & IMAP_ACL_ADMINISTER_FLAG)
     myrights += "a";
   
-  if (myrights.Length())
+  if (!myrights.IsEmpty())
     SetFolderRightsForUser(nsnull, myrights.get());
 }
 
@@ -5261,7 +5261,7 @@ const char *nsMsgIMAPFolderACL::GetRightsStringForUser(const char *inUserName)
 {
   nsXPIDLCString userName;
   userName.Assign(inUserName);
-  if (!userName.Length())
+  if (userName.IsEmpty())
   {
     nsCOMPtr <nsIMsgIncomingServer> server;
 
@@ -5437,49 +5437,49 @@ nsresult nsMsgIMAPFolderACL::CreateACLRightsString(PRUnichar **rightsString)
     }
     if (GetCanIWriteFolder())
     {
-      if (rights.Length()) rights += NS_LITERAL_STRING(", ");
+      if (!rights.IsEmpty()) rights += NS_LITERAL_STRING(", ");
       bundle->GetStringFromID(IMAP_ACL_WRITE_RIGHT, getter_Copies(curRight));
       rights.Append(curRight);
     }
     if (GetCanIInsertInFolder())
     {
-      if (rights.Length()) rights += NS_LITERAL_STRING(", ");
+      if (!rights.IsEmpty()) rights += NS_LITERAL_STRING(", ");
       bundle->GetStringFromID(IMAP_ACL_INSERT_RIGHT, getter_Copies(curRight));
       rights.Append(curRight);
     }
     if (GetCanILookupFolder())
     {
-      if (rights.Length()) rights += NS_LITERAL_STRING(", ");
+      if (!rights.IsEmpty()) rights += NS_LITERAL_STRING(", ");
       bundle->GetStringFromID(IMAP_ACL_LOOKUP_RIGHT, getter_Copies(curRight));
       rights.Append(curRight);
     }
     if (GetCanIStoreSeenInFolder())
     {
-      if (rights.Length()) rights += NS_LITERAL_STRING(", ");
+      if (!rights.IsEmpty()) rights += NS_LITERAL_STRING(", ");
       bundle->GetStringFromID(IMAP_ACL_SEEN_RIGHT, getter_Copies(curRight));
       rights.Append(curRight);
     }
     if (GetCanIDeleteInFolder())
     {
-      if (rights.Length()) rights += NS_LITERAL_STRING(", ");
+      if (!rights.IsEmpty()) rights += NS_LITERAL_STRING(", ");
       bundle->GetStringFromID(IMAP_ACL_DELETE_RIGHT, getter_Copies(curRight));
       rights.Append(curRight);
     }
     if (GetCanICreateSubfolder())
     {
-      if (rights.Length()) rights += NS_LITERAL_STRING(", ");
+      if (!rights.IsEmpty()) rights += NS_LITERAL_STRING(", ");
       bundle->GetStringFromID(IMAP_ACL_CREATE_RIGHT, getter_Copies(curRight));
       rights.Append(curRight);
     }
     if (GetCanIPostToFolder())
     {
-      if (rights.Length()) rights += NS_LITERAL_STRING(", ");
+      if (!rights.IsEmpty()) rights += NS_LITERAL_STRING(", ");
       bundle->GetStringFromID(IMAP_ACL_POST_RIGHT, getter_Copies(curRight));
       rights.Append(curRight);
     }
     if (GetCanIAdministerFolder())
     {
-      if (rights.Length()) rights += NS_LITERAL_STRING(", ");
+      if (!rights.IsEmpty()) rights += NS_LITERAL_STRING(", ");
       bundle->GetStringFromID(IMAP_ACL_ADMINISTER_RIGHT, getter_Copies(curRight));
       rights.Append(curRight);
     }
@@ -6955,7 +6955,7 @@ NS_IMETHODIMP nsImapMailFolder::RenameClient(nsIMsgWindow *msgWindow, nsIMsgFold
         if (imapFolder)
         {
           nsCAutoString onlineName(m_onlineFolderName); 
-          if (onlineName.Length() > 0)
+          if (!onlineName.IsEmpty())
           onlineName.Append(char(hierarchyDelimiter));
           onlineName.AppendWithConversion(folderNameStr);
           imapFolder->SetVerifiedAsOnlineFolder(PR_TRUE);
diff --git a/mozilla/mailnews/imap/src/nsImapProtocol.cpp b/mozilla/mailnews/imap/src/nsImapProtocol.cpp
index b1ca8efbe3e..753c88497b5 100644
--- a/mozilla/mailnews/imap/src/nsImapProtocol.cpp
+++ b/mozilla/mailnews/imap/src/nsImapProtocol.cpp
@@ -1844,7 +1844,7 @@ NS_IMETHODIMP nsImapProtocol::CanHandleUrl(nsIImapUrl * aImapUrl,
             {
               PRBool isInbox = 
                 PL_strcasecmp("Inbox", folderNameForProposedUrl) == 0;
-              if (curUrlFolderName.Length() > 0)
+              if (!curUrlFolderName.IsEmpty())
               {
                 PRBool matched = isInbox ?
                   PL_strcasecmp(curUrlFolderName.get(),
@@ -2252,14 +2252,14 @@ void nsImapProtocol::ProcessSelectedStateURL()
           m_runningUrl->CreateListOfMessageIdsString(getter_Copies(messageIdString));
           m_runningUrl->GetCustomAddFlags(getter_Copies(addFlags));
           m_runningUrl->GetCustomSubtractFlags(getter_Copies(subtractFlags));
-          if (addFlags.Length() > 0)
+          if (!addFlags.IsEmpty())
           {
             nsCAutoString storeString("+FLAGS (");
             storeString.Append(addFlags);
             storeString.Append(")");
             Store(messageIdString, storeString.get(), PR_TRUE);
           }
-          if (subtractFlags.Length() > 0)
+          if (!subtractFlags.IsEmpty())
           {
             nsCAutoString storeString("-FLAGS (");
             storeString.Append(subtractFlags);
@@ -3431,7 +3431,7 @@ void nsImapProtocol::ProcessMailboxUpdate(PRBool handlePossibleUndo)
       
       GetCurrentUrl()->CreateListOfMessageIdsString(getter_Copies(undoIdsStr));
       undoIds.Assign(undoIdsStr);
-      if (undoIds.Length() > 0)
+      if (!undoIds.IsEmpty())
       {
         char firstChar = (char) undoIds.CharAt(0);
         undoIds.Cut(0, 1);  // remove first character
@@ -4351,7 +4351,7 @@ nsImapProtocol::DiscoverMailboxSpec(nsImapMailboxSpec * adoptedBoxSpec)
           {
             SetConnectionStatus(-1);
           }
-          else if (boxNameCopy.Length() && 
+          else if (!boxNameCopy.IsEmpty() && 
             (GetMailboxDiscoveryStatus() == 
             eListMyChildren) &&
             (!useSubscription || GetSubscribingNow()))
@@ -4364,7 +4364,7 @@ nsImapProtocol::DiscoverMailboxSpec(nsImapMailboxSpec * adoptedBoxSpec)
           {
             if (m_hierarchyNameState ==
               kListingForInfoAndDiscovery &&
-              boxNameCopy.Length() && 
+              !boxNameCopy.IsEmpty() && 
               !(adoptedBoxSpec->box_flags & kNameSpace))
             {
               // remember the info here also
@@ -5189,7 +5189,7 @@ void nsImapProtocol::UploadMessageFromFile (nsIFileSpec* fileSpec,
           rv = m_imapExtensionSink->GetMessageId(this, &messageId,
             m_runningUrl);
           WaitForFEEventCompletion();
-          if (NS_SUCCEEDED(rv) && messageId.Length() > 0 &&
+          if (NS_SUCCEEDED(rv) && !messageId.IsEmpty() &&
             GetServerStateParser().LastCommandSuccessful())
           {
             // if the appended to folder isn't selected in the connection,
@@ -5846,7 +5846,7 @@ PRBool nsImapProtocol::DeleteSubFolders(const char* selectedMailbox, PRBool &aDe
         pattern.Append(onlineDirSeparator);
         pattern.Append('*');
 
-    if (pattern.Length())
+    if (!pattern.IsEmpty())
     {
       List(pattern.get(), PR_FALSE);
     }
@@ -6100,7 +6100,7 @@ void nsImapProtocol::OnMoveFolderHierarchy(const char * sourceMailbox)
         else
             oldBoxName.Right(leafName, length-(leafStart+1));
 
-        if ( newBoxName.Length() > 0 )
+        if ( !newBoxName.IsEmpty() )
              newBoxName.Append(onlineDirSeparator);
         newBoxName.Append(leafName);
         PRBool  renamed = RenameHierarchyByHand(sourceMailbox,
@@ -6240,17 +6240,17 @@ void nsImapProtocol::DiscoverAllAndSubscribedBoxes()
     			nsCOMPtr<nsIImapIncomingServer> imapServer = do_QueryReferent(m_server, &rv);
 				if (NS_FAILED(rv) || !imapServer) return;
 
-				if (allPattern.Length())
+				if (!allPattern.IsEmpty())
 				{
 					imapServer->SetDoingLsub(PR_TRUE);
 					Lsub(allPattern.get(), PR_TRUE);	// LSUB all the subscribed
 				}
-				if (topLevelPattern.Length())
+				if (!topLevelPattern.IsEmpty())
 				{
 					imapServer->SetDoingLsub(PR_FALSE);
 					List(topLevelPattern.get(), PR_TRUE);	// LIST the top level
 				}
-				if (secondLevelPattern.Length())
+				if (!secondLevelPattern.IsEmpty())
 				{
 					imapServer->SetDoingLsub(PR_FALSE);
 					List(secondLevelPattern.get(), PR_TRUE);	// LIST the second level
@@ -7035,7 +7035,7 @@ void nsImapProtocol::SetupMessageFlagsString(nsCString& flagString,
       flagString.Append(" ");
     }
     // eat the last space
-    if (flagString.Length() > 0)
+    if (!flagString.IsEmpty())
         flagString.SetLength(flagString.Length()-1);
 }
 
@@ -7836,7 +7836,7 @@ nsresult nsImapMockChannel::ReadFromMemCache(nsICacheEntryDescriptor *entry)
   if (entryKey.FindChar('?') != kNotFound)
   {
     entry->GetMetaDataElement("contentType", getter_Copies(contentType));
-    if (contentType.Length() > 0)
+    if (!contentType.IsEmpty())
       SetContentType(contentType);
     shouldUseCacheEntry = PR_TRUE;
   }
diff --git a/mozilla/mailnews/imap/src/nsImapServerResponseParser.cpp b/mozilla/mailnews/imap/src/nsImapServerResponseParser.cpp
index 04daee492d4..2fa50617499 100644
--- a/mozilla/mailnews/imap/src/nsImapServerResponseParser.cpp
+++ b/mozilla/mailnews/imap/src/nsImapServerResponseParser.cpp
@@ -420,7 +420,7 @@ void nsImapServerResponseParser::ProcessOkCommand(const char *commandToken)
 	}
 	else if (!PL_strcasecmp(commandToken, "FETCH"))
 	{
-		if (fZeroLengthMessageUidString.Length())
+		if (!fZeroLengthMessageUidString.IsEmpty())
 		{
 			// "Deleting zero length message");
 			fServerConnection.Store(fZeroLengthMessageUidString.get(), "+Flags (\\Deleted)", PR_TRUE);
@@ -1199,13 +1199,10 @@ void nsImapServerResponseParser::msg_fetch()
 					char uidString[100];
 					sprintf(uidString, "%ld", (long)CurrentResponseUID());
 					
-					if (!fZeroLengthMessageUidString.Length())
-						fZeroLengthMessageUidString = uidString;
-					else
-					{
+					if (!fZeroLengthMessageUidString.IsEmpty())
 						fZeroLengthMessageUidString += ",";
-						fZeroLengthMessageUidString += uidString;
-					}
+
+                    fZeroLengthMessageUidString += uidString;
 				}
 				
 				// if this token ends in ')', then it is the last token
@@ -1379,7 +1376,7 @@ void nsImapServerResponseParser::envelope_data()
 				nsCAutoString address;
 				parse_address(address);
 				headerLine += address;
-				if (address.Length() == 0)
+				if (address.IsEmpty())
 					headerNonNil = PR_FALSE;
 			}
 			if (headerNonNil)
diff --git a/mozilla/mailnews/imap/src/nsImapUndoTxn.cpp b/mozilla/mailnews/imap/src/nsImapUndoTxn.cpp
index a50a117c014..9fa8419e355 100644
--- a/mozilla/mailnews/imap/src/nsImapUndoTxn.cpp
+++ b/mozilla/mailnews/imap/src/nsImapUndoTxn.cpp
@@ -365,7 +365,7 @@ nsresult
 nsImapMoveCopyMsgTxn::AddDstKey(nsMsgKey aKey)
 {
     m_dstKeyArray.Add(aKey);
-    if (m_dstMsgIdString.Length() > 0)
+    if (!m_dstMsgIdString.IsEmpty())
         m_dstMsgIdString.Append(",");
     m_dstMsgIdString.AppendInt((PRInt32) aKey);
     return NS_OK;
diff --git a/mozilla/mailnews/imap/src/nsImapUrl.cpp b/mozilla/mailnews/imap/src/nsImapUrl.cpp
index 9a7897f7b25..9e445591a4d 100644
--- a/mozilla/mailnews/imap/src/nsImapUrl.cpp
+++ b/mozilla/mailnews/imap/src/nsImapUrl.cpp
@@ -1038,7 +1038,7 @@ NS_IMETHODIMP nsImapUrl::AllocateCanonicalPath(const char *serverPath, char onli
 	// If this host has an online server directory configured
 	onlineDir = (char *)(!aString.IsEmpty() ? ToNewCString(aString) : nsnull);
 
-	if (currentPath && onlineDir.Length() > 0)
+	if (currentPath && !onlineDir.IsEmpty())
 	{
 		// By definition, the online dir must be at the root.
 		if (delimiterToUse && delimiterToUse != kOnlineHierarchySeparatorUnknown)
diff --git a/mozilla/mailnews/import/eudora/src/nsEudoraAddress.cpp b/mozilla/mailnews/import/eudora/src/nsEudoraAddress.cpp
index 8391db44545..fab3bb3bc24 100644
--- a/mozilla/mailnews/import/eudora/src/nsEudoraAddress.cpp
+++ b/mozilla/mailnews/import/eudora/src/nsEudoraAddress.cpp
@@ -437,7 +437,7 @@ PRBool CAliasData::Process( const char *pLine, PRInt32 len)
 		if (*pLine == '"') {
 			if (tCnt && !endCollect) {
 				str.Trim( kWhitespace);
-				if (str.Length())
+				if (!str.IsEmpty())
 					str.Append( " ", 1);
 				str.Append( pStart, tCnt);
 			}
@@ -453,7 +453,7 @@ PRBool CAliasData::Process( const char *pLine, PRInt32 len)
 		else if (*pLine == '<') {
 			if (tCnt && !endCollect) {
 				str.Trim( kWhitespace);
-				if (str.Length())
+				if (!str.IsEmpty())
 					str.Append( " ", 1);
 				str.Append( pStart, tCnt);
 			}
@@ -470,7 +470,7 @@ PRBool CAliasData::Process( const char *pLine, PRInt32 len)
 		else if (*pLine == '(') {
 			if (tCnt && !endCollect) {
 				str.Trim( kWhitespace);
-				if (str.Length())
+				if (!str.IsEmpty())
 					str.Append( " ", 1);
 				str.Append( pStart, tCnt);
 			}
@@ -495,27 +495,27 @@ PRBool CAliasData::Process( const char *pLine, PRInt32 len)
 	
 	if (tCnt) {
 		str.Trim( kWhitespace);
-		if (str.Length())
+		if (!str.IsEmpty())
 			str.Append( " ", 1);
 		str.Append( pStart, tCnt);
 	}
 	
 	str.Trim( kWhitespace);
 	
-	if (m_realName.Length() && m_email.Length())
+	if (!m_realName.IsEmpty() && !m_email.IsEmpty())
 		return( PR_TRUE);
 	
 	// now we should have a string with any remaining non-delimitted text
 	// we assume that the last token is the email
 	// anything before that is realName
-	if (m_email.Length()) {
+	if (!m_email.IsEmpty()) {
 		m_realName = str;
 		return( PR_TRUE);
 	}
 	
 	tCnt = str.RFindChar( ' ');
 	if (tCnt == -1) {
-		if (str.Length()) {
+		if (!str.IsEmpty()) {
 			m_email = str;
 			return( PR_TRUE);
 		}
@@ -527,7 +527,7 @@ PRBool CAliasData::Process( const char *pLine, PRInt32 len)
 	m_realName.Trim( kWhitespace);
 	m_email.Trim( kWhitespace);
 	
-	return( (m_email.Length() != 0));
+	return( !m_email.IsEmpty());
 }
 
 #ifdef IMPORT_DEBUG
@@ -738,7 +738,7 @@ void nsEudoraAddress::AddSingleCard( CAliasEntry *pEntry, nsVoidArray &emailList
   nsCString	addressWK, address2WK, cityWK, stateWK, zipWK, countryWK;
 	nsCString	note(pEntry->m_notes);
 
-	if (note.Length() > 0)
+	if (!note.IsEmpty())
   {
 		ExtractNoteField( note, fax, "fax");
 		ExtractNoteField( note, phone, "phone");
diff --git a/mozilla/mailnews/import/eudora/src/nsEudoraCompose.cpp b/mozilla/mailnews/import/eudora/src/nsEudoraCompose.cpp
index 004c603c735..83460a180c6 100644
--- a/mozilla/mailnews/import/eudora/src/nsEudoraCompose.cpp
+++ b/mozilla/mailnews/import/eudora/src/nsEudoraCompose.cpp
@@ -598,13 +598,13 @@ nsresult nsEudoraCompose::SendTheMessage( nsIFileSpec *pMsg)
 	nsString	charSet;
 	nsString	headerVal;
 	GetHeaderValue( m_pHeaders, m_headerLen, "From:", headerVal);
-	if (headerVal.Length())
+	if (!headerVal.IsEmpty())
 		m_pMsgFields->SetFrom( headerVal.get());
 	GetHeaderValue( m_pHeaders, m_headerLen, "To:", headerVal);
-	if (headerVal.Length())
+	if (!headerVal.IsEmpty())
 		m_pMsgFields->SetTo( headerVal.get());
 	GetHeaderValue( m_pHeaders, m_headerLen, "Subject:", headerVal);
-	if (headerVal.Length())
+	if (!headerVal.IsEmpty())
 		m_pMsgFields->SetSubject( headerVal.get());
 	GetHeaderValue( m_pHeaders, m_headerLen, "Content-type:", headerVal);
 	bodyType = headerVal;
@@ -613,12 +613,12 @@ nsresult nsEudoraCompose::SendTheMessage( nsIFileSpec *pMsg)
   // Use platform charset as default if the msg doesn't specify one
   // (ie, no 'charset' param in the Content-Type: header). As the last
   // resort we'll use the mail defaul charset.
-  if (! headerVal.Length())
+  if (headerVal.IsEmpty())
   {
     headerVal.AssignWithConversion(nsMsgI18NFileSystemCharset());
-    if (! headerVal.Length())
+    if (headerVal.IsEmpty())
     { // last resort
-      if (!m_defCharset.Length())
+      if (m_defCharset.IsEmpty())
       {
         nsXPIDLString defaultCharset;
         nsCOMPtr<nsIPref> prefs(do_GetService(NS_PREF_CONTRACTID, &rv));
@@ -632,18 +632,18 @@ nsresult nsEudoraCompose::SendTheMessage( nsIFileSpec *pMsg)
   m_pMsgFields->SetCharacterSet( NS_LossyConvertUCS2toASCII(headerVal).get() );
   charSet = headerVal;
 	GetHeaderValue( m_pHeaders, m_headerLen, "CC:", headerVal);
-	if (headerVal.Length())
+	if (!headerVal.IsEmpty())
 		m_pMsgFields->SetCc( headerVal.get());
 	GetHeaderValue( m_pHeaders, m_headerLen, "Message-ID:", headerVal);
-	if (headerVal.Length())
+	if (!headerVal.IsEmpty())
 		m_pMsgFields->SetMessageId( NS_LossyConvertUCS2toASCII(headerVal).get() );
 	GetHeaderValue( m_pHeaders, m_headerLen, "Reply-To:", headerVal);
-	if (headerVal.Length())
+	if (!headerVal.IsEmpty())
 		m_pMsgFields->SetReplyTo( headerVal.get());
 
 	// what about all of the other headers?!?!?!?!?!?!
 	char *pMimeType = nsnull;
-	if (bodyType.Length())
+	if (!bodyType.IsEmpty())
 		pMimeType = ToNewCString(bodyType);
 	
 	// IMPORT_LOG0( "Outlook compose calling CreateAndSendMessage\n");
@@ -1083,7 +1083,7 @@ nsresult nsEudoraCompose::WriteHeaders( nsIFileSpec *pDst, SimpleBufferTonyRCopi
 	do {
 		GetNthHeader( m_pHeaders, m_headerLen, n, header, val, PR_FALSE);
 		// GetNthHeader( newHeaders.m_pBuffer, newHeaders.m_writeOffset, n, header, val, PR_FALSE);
-		if (header.Length()) {
+		if (!header.IsEmpty()) {
 			if ((specialHeader = IsSpecialHeader( header.get())) != -1) {
 				header.Append( ':');
 				GetHeaderValue( newHeaders.m_pBuffer, newHeaders.m_writeOffset - 1, header.get(), val, PR_FALSE);
@@ -1095,10 +1095,10 @@ nsresult nsEudoraCompose::WriteHeaders( nsIFileSpec *pDst, SimpleBufferTonyRCopi
 				header.Append( ':');
 				GetHeaderValue( newHeaders.m_pBuffer, newHeaders.m_writeOffset - 1, header.get(), replaceVal, PR_FALSE);
 				header.Truncate( header.Length() - 1);
-				if (replaceVal.Length())
+				if (!replaceVal.IsEmpty())
 					val = replaceVal;
 			}
-			if (val.Length()) {
+			if (!val.IsEmpty()) {
         // See if we're writing out a Date: header.
         if (!nsCRT::strcasecmp(header.get(), "Date"))
           hasDateHeader = PR_TRUE;
@@ -1113,7 +1113,7 @@ nsresult nsEudoraCompose::WriteHeaders( nsIFileSpec *pDst, SimpleBufferTonyRCopi
 			}
 		}
 		n++;
-	} while (NS_SUCCEEDED( rv) && (header.Length() != 0));
+	} while (NS_SUCCEEDED( rv) && !header.IsEmpty());
 
   // If we don't have Date: header so far then use the default one (taken from Eudora "From " line).
   if (!hasDateHeader)
@@ -1129,7 +1129,7 @@ nsresult nsEudoraCompose::WriteHeaders( nsIFileSpec *pDst, SimpleBufferTonyRCopi
 			header.Append( ':');
 			GetHeaderValue( newHeaders.m_pBuffer, newHeaders.m_writeOffset - 1, header.get(), val, PR_FALSE);
 			header.Truncate( header.Length() - 1);
-			if (val.Length()) {
+			if (!val.IsEmpty()) {
 				rv = pDst->Write( header.get(), header.Length(), &written);
 				if (NS_SUCCEEDED( rv))
 					rv = pDst->Write( ": ", 2, &written);
diff --git a/mozilla/mailnews/import/eudora/src/nsEudoraWin32.cpp b/mozilla/mailnews/import/eudora/src/nsEudoraWin32.cpp
index ed51951b35b..bff63c0bbce 100644
--- a/mozilla/mailnews/import/eudora/src/nsEudoraWin32.cpp
+++ b/mozilla/mailnews/import/eudora/src/nsEudoraWin32.cpp
@@ -383,7 +383,7 @@ nsresult nsEudoraWin32::ScanDescmap( nsIFileSpec *pFolder, nsISupportsArray *pAr
 
 		IMPORT_LOG2( "name: %s, fName: %s\n", name.get(), fName.get());
 
-		if (fName.Length() && name.Length() && (type.Length() == 1)) {
+		if (!fName.IsEmpty() && !name.IsEmpty() && (type.Length() == 1)) {
 			entry->FromFileSpec( pFolder);
 			rv = entry->AppendRelativeUnixPath( fName.get());
 			if (NS_SUCCEEDED( rv)) {
@@ -583,7 +583,7 @@ PRBool nsEudoraWin32::ImportSettings( nsIFileSpec *pIniFile, nsIMsgAccount **loc
 	nsIMsgAccount *	pAccount;
 
 	do {
-		if (sectionName.Length()) {
+		if (!sectionName.IsEmpty()) {
 			pAccount = nsnull;
 			valInt = ::GetPrivateProfileInt( sectionName.get(), "UsesPOP", 1, iniPath.get());
 			if (valInt) {
@@ -721,7 +721,7 @@ PRBool nsEudoraWin32::BuildPOPAccount( nsIMsgAccountManager *accMgr, const char
 	
 	GetServerAndUserName( pSection, pIni, serverName, userName, valBuff);
 	
-	if (!serverName.Length() || !userName.Length())
+	if (serverName.IsEmpty() || userName.IsEmpty())
 		return( PR_FALSE);
 
 	PRBool	result = PR_FALSE;
@@ -783,7 +783,7 @@ PRBool nsEudoraWin32::BuildIMAPAccount( nsIMsgAccountManager *accMgr, const char
 	
 	GetServerAndUserName( pSection, pIni, serverName, userName, valBuff);
 	
-	if (!serverName.Length() || !userName.Length())
+	if (serverName.IsEmpty() || userName.IsEmpty())
 		return( PR_FALSE);
 
 	PRBool	result = PR_FALSE;
@@ -857,7 +857,7 @@ void nsEudoraWin32::SetIdentities(nsIMsgAccountManager *accMgr, nsIMsgAccount *a
 		fullName.AssignWithConversion(realName.get());
 		id->SetFullName( fullName.get());
 		id->SetIdentityName( fullName.get());
-		if (email.Length() == 0) {
+		if (email.IsEmpty()) {
 			email = userName;
 			email += "@";
 			email += serverName;
@@ -927,7 +927,7 @@ nsresult nsEudoraWin32::GetAttachmentInfo( const char *pFileName, nsIFileSpec *p
 				GetMimeTypeFromExtension( ext, mimeType);
 			}
 		}
-		if (!mimeType.Length())
+		if (mimeType.IsEmpty())
 			mimeType = "application/octet-stream";
 
 		return( NS_OK);
@@ -1022,7 +1022,7 @@ void nsEudoraWin32::GetMimeTypeFromExtension( nsCString& ext, nsCString& mimeTyp
 		::RegCloseKey( sKey);
 	}
 
-	if (mimeType.Length() || !m_mailImportLocation || (ext.Length() > 10))
+	if (!mimeType.IsEmpty() || !m_mailImportLocation || (ext.Length() > 10))
 		return;
 	
 	// TLR: FIXME: We should/could cache the extension to mime type maps we find
@@ -1127,7 +1127,7 @@ void nsEudoraWin32::GetMimeTypeFromExtension( nsCString& ext, nsCString& mimeTyp
 			tStr.Truncate();
 			tStr.Append( pStart, len);
 			tStr.Trim( kWhitespace);
-			if (!tStr.Length()) continue;
+			if (tStr.IsEmpty()) continue;
 			mimeType.Truncate();
 			mimeType.Append( tStr.get());
 			mimeType.Append( "/");
@@ -1141,7 +1141,7 @@ void nsEudoraWin32::GetMimeTypeFromExtension( nsCString& ext, nsCString& mimeTyp
 			tStr.Truncate();
 			tStr.Append( pStart, len);
 			tStr.Trim( kWhitespace);
-			if (!tStr.Length()) continue;
+			if (tStr.IsEmpty()) continue;
 			mimeType.Append( tStr.get());
 
 			IMPORT_LOG1( "Found Mime Type: %s\n", mimeType.get());
@@ -1261,7 +1261,7 @@ nsresult nsEudoraWin32::FindAddressBooks( nsIFileSpec *pRoot, nsISupportsArray *
 	while ((idx = dirs.FindChar( ';')) != -1) {
 		dirs.Left( currentDir, idx);
 		currentDir.Trim( kWhitespace);
-		if (currentDir.Length()) {
+		if (!currentDir.IsEmpty()) {
 			rv = spec->SetNativePath( currentDir.get());
 			exists = PR_FALSE;
 			isDir = PR_FALSE;
@@ -1278,7 +1278,7 @@ nsresult nsEudoraWin32::FindAddressBooks( nsIFileSpec *pRoot, nsISupportsArray *
 		dirs = currentDir;
 		dirs.Trim( kWhitespace);
 	}
-	if (dirs.Length()) {
+	if (!dirs.IsEmpty()) {
 		rv = spec->SetNativePath( dirs.get());
 		exists = PR_FALSE;
 		isDir = PR_FALSE;
diff --git a/mozilla/mailnews/import/oexpress/nsOEScanBoxes.cpp b/mozilla/mailnews/import/oexpress/nsOEScanBoxes.cpp
index aa906154e8b..09da8c7e2e3 100644
--- a/mozilla/mailnews/import/oexpress/nsOEScanBoxes.cpp
+++ b/mozilla/mailnews/import/oexpress/nsOEScanBoxes.cpp
@@ -796,7 +796,7 @@ void nsOEScanBoxes::BuildMailboxList( MailboxEntry *pBox, nsIFileSpec * root, PR
 			pID->SetDepth( depth);
 			pID->SetIdentifier( pBox->index);
 			pID->SetDisplayName( (PRUnichar *)pBox->mailName.get());
-			if (pBox->fileName.Length() > 0) {
+			if (!pBox->fileName.IsEmpty()) {
 				pID->GetFileSpec( &file);
 				file->FromFileSpec( root);
 				file->AppendRelativeUnixPath( pBox->fileName.get());
diff --git a/mozilla/mailnews/import/outlook/src/nsOutlookCompose.cpp b/mozilla/mailnews/import/outlook/src/nsOutlookCompose.cpp
index 11102c0c76c..75a466c67c5 100644
--- a/mozilla/mailnews/import/outlook/src/nsOutlookCompose.cpp
+++ b/mozilla/mailnews/import/outlook/src/nsOutlookCompose.cpp
@@ -593,13 +593,13 @@ nsresult nsOutlookCompose::SendTheMessage( nsIFileSpec *pMsg, nsMsgDeliverMode m
     nsCAutoString asciiHeaderVal;
 
 	GetHeaderValue( m_Headers.get(), m_Headers.Length(), "From:", headerVal);
-	if (headerVal.Length())
+	if (!headerVal.IsEmpty())
 		m_pMsgFields->SetFrom( headerVal.get());
 	GetHeaderValue( m_Headers.get(), m_Headers.Length(), "To:", headerVal);
-	if (headerVal.Length())
+	if (!headerVal.IsEmpty())
 		m_pMsgFields->SetTo( headerVal.get());
 	GetHeaderValue( m_Headers.get(), m_Headers.Length(), "Subject:", headerVal);
-	if (headerVal.Length())
+	if (!headerVal.IsEmpty())
 		m_pMsgFields->SetSubject( headerVal.get());
 	GetHeaderValue( m_Headers.get(), m_Headers.Length(), "Content-type:", headerVal);
 
@@ -630,20 +630,20 @@ nsresult nsOutlookCompose::SendTheMessage( nsIFileSpec *pMsg, nsMsgDeliverMode m
   m_pMsgFields->SetCharacterSet( NS_LossyConvertUCS2toASCII(headerVal).get() );
   charSet = headerVal;
 	GetHeaderValue( m_Headers.get(), m_Headers.Length(), "CC:", headerVal);
-	if (headerVal.Length())
+	if (!headerVal.IsEmpty())
 		m_pMsgFields->SetCc( headerVal.get());
 	GetHeaderValue( m_Headers.get(), m_Headers.Length(), "Message-ID:", headerVal);
-	if (headerVal.Length()) {
+	if (!headerVal.IsEmpty()) {
         asciiHeaderVal.AssignWithConversion(headerVal);
 		m_pMsgFields->SetMessageId(asciiHeaderVal.get());
     }
 	GetHeaderValue( m_Headers.get(), m_Headers.Length(), "Reply-To:", headerVal);
-	if (headerVal.Length())
+	if (!headerVal.IsEmpty())
 		m_pMsgFields->SetReplyTo( headerVal.get());
 
 	// what about all of the other headers?!?!?!?!?!?!
 	char *pMimeType = nsnull;
-	if (bodyType.Length())
+	if (!bodyType.IsEmpty())
 		pMimeType = ToNewCString(bodyType);
 	
 	// IMPORT_LOG0( "Outlook compose calling CreateAndSendMessage\n");
@@ -1023,7 +1023,7 @@ nsresult nsOutlookCompose::WriteHeaders( nsIFileSpec *pDst, SimpleBufferTonyRCop
 	do {
 		GetNthHeader( m_Headers.get(), m_Headers.Length(), n, header, val, PR_FALSE);
 		// GetNthHeader( newHeaders.m_pBuffer, newHeaders.m_writeOffset, n, header.get(), val, PR_FALSE);
-		if (header.Length()) {
+		if (!header.IsEmpty()) {
 			if ((specialHeader = IsSpecialHeader( header.get())) != -1) {
 				header.Append( ':');
 				GetHeaderValue( newHeaders.m_pBuffer, newHeaders.m_writeOffset - 1, header.get(), val, PR_FALSE);
@@ -1039,10 +1039,10 @@ nsresult nsOutlookCompose::WriteHeaders( nsIFileSpec *pDst, SimpleBufferTonyRCop
 				header.Append( ':');
 				GetHeaderValue( newHeaders.m_pBuffer, newHeaders.m_writeOffset - 1, header.get(), replaceVal, PR_FALSE);
 				header.Truncate( header.Length() - 1);
-				if (replaceVal.Length())
+				if (!replaceVal.IsEmpty())
 					val = replaceVal;
 			}
-			if (val.Length()) {
+			if (!val.IsEmpty()) {
 				rv = pDst->Write( header.get(), header.Length(), &written);
 				if (NS_SUCCEEDED( rv))
 					rv = pDst->Write( ": ", 2, &written);
@@ -1054,7 +1054,7 @@ nsresult nsOutlookCompose::WriteHeaders( nsIFileSpec *pDst, SimpleBufferTonyRCop
 			}
 		}
 		n++;
-	} while (NS_SUCCEEDED( rv) && (header.Length() != 0));
+	} while (NS_SUCCEEDED( rv) && !header.IsEmpty());
 
 	for (i = 0; (i < kMaxSpecialHeaders) && NS_SUCCEEDED( rv); i++) {
 		if (!specials[i]) {
@@ -1062,7 +1062,7 @@ nsresult nsOutlookCompose::WriteHeaders( nsIFileSpec *pDst, SimpleBufferTonyRCop
 			header.Append( ':');
 			GetHeaderValue( newHeaders.m_pBuffer, newHeaders.m_writeOffset - 1, header.get(), val, PR_FALSE);
 			header.Truncate( header.Length() - 1);
-			if (val.Length()) {
+			if (!val.IsEmpty()) {
 				rv = pDst->Write( header.get(), header.Length(), &written);
 				if (NS_SUCCEEDED( rv))
 					rv = pDst->Write( ": ", 2, &written);
diff --git a/mozilla/mailnews/import/text/src/nsTextAddress.cpp b/mozilla/mailnews/import/text/src/nsTextAddress.cpp
index 1b1d1e6f237..68631d43bb4 100644
--- a/mozilla/mailnews/import/text/src/nsTextAddress.cpp
+++ b/mozilla/mailnews/import/text/src/nsTextAddress.cpp
@@ -496,7 +496,7 @@ nsresult nsTextAddress::ProcessLine( const char *pLine, PRInt32 len, nsString& e
             rv = m_fieldMap->GetFieldActive( i, &active);
         if (NS_SUCCEEDED( rv) && active) {
             if (GetField( pLine, len, i, fieldVal, m_delim)) {
-                if (fieldVal.Length()) {
+                if (!fieldVal.IsEmpty()) {
                     if (!newRow) {
                         rv = m_database->GetNewRow( &newRow);
                         if (NS_FAILED( rv)) {
@@ -889,7 +889,7 @@ nsresult nsTextAddress::ParseLdifFile( nsIFileSpec *pSrc, PRUint32 *pProgress)
 
             while (NS_SUCCEEDED(GetLdifStringRecord(buf, len, startPos)))
             {
-                 if (m_ldifLine.Find("groupOfNames") == -1)
+                 if (m_ldifLine.Find("groupOfNames") == kNotFound)
                     AddLdifRowToDatabase(PR_FALSE);
                 else
                 {
@@ -905,7 +905,7 @@ nsresult nsTextAddress::ParseLdifFile( nsIFileSpec *pSrc, PRUint32 *pProgress)
         }
     }
     //last row
-    if (m_ldifLine.Length() > 0 && m_ldifLine.Find("groupOfNames") == -1)
+    if (!m_ldifLine.IsEmpty() && m_ldifLine.Find("groupOfNames") == kNotFound)
         AddLdifRowToDatabase(PR_FALSE); 
 
     // mail Lists
@@ -929,7 +929,7 @@ nsresult nsTextAddress::ParseLdifFile( nsIFileSpec *pSrc, PRUint32 *pProgress)
 
                 while (NS_SUCCEEDED(GetLdifStringRecord(listBuf, len, startPos)))
                 {
-                    if (m_ldifLine.Find("groupOfNames") != -1)
+                    if (m_ldifLine.Find("groupOfNames") != kNotFound)
                     {
                         AddLdifRowToDatabase(PR_TRUE);
                         if (NS_SUCCEEDED(pSrc->Seek(0)))
@@ -993,7 +993,7 @@ void nsTextAddress::AddLdifRowToDatabase(PRBool bIsList)
 
 void nsTextAddress::ClearLdifRecordBuffer()
 {
-  if (m_ldifLine.Length() > 0)
+  if (!m_ldifLine.IsEmpty())
   {
       m_ldifLine.Truncate();
       m_LFCount = 0;
diff --git a/mozilla/mailnews/local/src/nsLocalMailFolder.cpp b/mozilla/mailnews/local/src/nsLocalMailFolder.cpp
index 6f137ea6cc0..5c797c7d8ba 100644
--- a/mozilla/mailnews/local/src/nsLocalMailFolder.cpp
+++ b/mozilla/mailnews/local/src/nsLocalMailFolder.cpp
@@ -881,7 +881,7 @@ nsMsgLocalMailFolder::CreateSubfolder(const PRUnichar *folderName, nsIMsgWindow
   nsXPIDLCString nativeFolderName;
   rv = ConvertFromUnicode(nsMsgI18NFileSystemCharset(), nsAutoString(folderName),
                      getter_Copies(nativeFolderName));
-  if (NS_FAILED(rv) || (nativeFolderName.Length() == 0)) {
+  if (NS_FAILED(rv) || nativeFolderName.IsEmpty()) {
      ThrowAlertMsg("folderCreationFailed", msgWindow);
      // I'm returning this value so the dialog stays up
      return NS_MSG_FOLDER_EXISTS;
diff --git a/mozilla/mailnews/local/src/nsLocalUndoTxn.cpp b/mozilla/mailnews/local/src/nsLocalUndoTxn.cpp
index af3fb9ac318..903c386505a 100644
--- a/mozilla/mailnews/local/src/nsLocalUndoTxn.cpp
+++ b/mozilla/mailnews/local/src/nsLocalUndoTxn.cpp
@@ -187,7 +187,7 @@ nsLocalMoveCopyMsgTxn::UndoImapDeleteFlag(nsIMsgFolder* folder,
 
             for (i=0; i < count; i++)
             {
-                if (msgIds.Length() > 0)
+                if (!msgIds.IsEmpty())
                     msgIds.Append(',');
                 msgIds.AppendInt((PRInt32) keyArray.GetAt(i));
             }
diff --git a/mozilla/mailnews/local/src/nsPop3URL.cpp b/mozilla/mailnews/local/src/nsPop3URL.cpp
index 01f960c7b58..ec184868a54 100644
--- a/mozilla/mailnews/local/src/nsPop3URL.cpp
+++ b/mozilla/mailnews/local/src/nsPop3URL.cpp
@@ -82,7 +82,7 @@ nsresult nsPop3URL::GetPop3Sink(nsIPop3Sink** aPop3Sink)
 NS_IMETHODIMP
 nsPop3URL::GetMessageUri(char ** aMessageUri)
 {
-    if(!aMessageUri || m_messageUri.Length() == 0)
+    if(!aMessageUri || m_messageUri.IsEmpty())
         return NS_ERROR_NULL_POINTER;
     *aMessageUri = ToNewCString(m_messageUri);
     return NS_OK;
diff --git a/mozilla/mailnews/mapi/mapihook/src/msgMapiHook.cpp b/mozilla/mailnews/mapi/mapihook/src/msgMapiHook.cpp
index ea117567c76..cbce2d2c9a7 100644
--- a/mozilla/mailnews/mapi/mapihook/src/msgMapiHook.cpp
+++ b/mozilla/mailnews/mapi/mapihook/src/msgMapiHook.cpp
@@ -443,19 +443,19 @@ nsresult nsMapiHook::PopulateCompFields(lpnsMapiMessage aMessage,
                 switch (aMessage->lpRecips[i].ulRecipClass)
                 {
                 case MAPI_TO :
-                    if (To.Length() > 0)
+                    if (!To.IsEmpty())
                         To += Comma ;
                     To += (PRUnichar *) aMessage->lpRecips[i].lpszAddress ;
                     break ;
 
                 case MAPI_CC :
-                    if (Cc.Length() > 0)
+                    if (!Cc.IsEmpty())
                         Cc += Comma ;
-                    Cc += (PRUnichar *) aMessage->lpRecips[i].lpszAddress ; 
+                    Cc += (PRUnichar *) aMessage->lpRecips[i].lpszAddress ;
                     break ;
 
                 case MAPI_BCC :
-                    if (Bcc.Length() > 0)
+                    if (!Bcc.IsEmpty())
                         Bcc += Comma ;
                     Bcc += (PRUnichar *) aMessage->lpRecips[i].lpszAddress ; 
                     break ;
@@ -681,19 +681,19 @@ nsresult nsMapiHook::PopulateCompFieldsWithConversion(lpnsMapiMessage aMessage,
                 switch (aMessage->lpRecips[i].ulRecipClass)
                 {
                 case MAPI_TO :
-                    if (To.Length() > 0)
+                    if (!To.IsEmpty())
                         To += Comma ;
                     To.AppendWithConversion ((char *) aMessage->lpRecips[i].lpszAddress);
                     break ;
 
                 case MAPI_CC :
-                    if (Cc.Length() > 0)
+                    if (!Cc.IsEmpty())
                         Cc += Comma ;
-                    Cc.AppendWithConversion ((char *) aMessage->lpRecips[i].lpszAddress); 
+                    Cc.AppendWithConversion ((char *) aMessage->lpRecips[i].lpszAddress);
                     break ;
 
                 case MAPI_BCC :
-                    if (Bcc.Length() > 0)
+                    if (!Bcc.IsEmpty())
                         Bcc += Comma ;
                     Bcc.AppendWithConversion ((char *) aMessage->lpRecips[i].lpszAddress) ; 
                     break ;
@@ -777,7 +777,7 @@ nsresult nsMapiHook::PopulateCompFieldsForSendDocs(nsIMsgCompFields * aCompField
     nsCString Attachments ;
 
     // only 1 file is to be sent, no delim specified
-    if ((!strDelimChars.Length()) && (strFilePaths.Length()>0))
+    if (strDelimChars.IsEmpty() && !strFilePaths.IsEmpty())
     {
         nsCOMPtr <nsILocalFile> pFile = do_CreateInstance (NS_LOCAL_FILE_CONTRACTID, &rv) ;
         if (NS_FAILED(rv) || (!pFile) ) return rv ;        
@@ -830,7 +830,7 @@ nsresult nsMapiHook::PopulateCompFieldsForSendDocs(nsIMsgCompFields * aCompField
             NS_GetURLSpecFromFile(pFile, pURL);
             if (!pURL.IsEmpty())
             {
-                if (Attachments.Length() > 0)
+                if (!Attachments.IsEmpty())
                     Attachments.Append(",") ;
                 Attachments.Append(pURL) ;
             }
diff --git a/mozilla/modules/libjar/nsJAR.cpp b/mozilla/modules/libjar/nsJAR.cpp
index 35426b4cfd0..ef0638c51aa 100644
--- a/mozilla/modules/libjar/nsJAR.cpp
+++ b/mozilla/modules/libjar/nsJAR.cpp
@@ -701,7 +701,7 @@ nsJAR::ParseOneFile(nsISignatureVerifier* verifier,
             curItemSF->status = mGlobalStatus;
             if (curItemSF->status == nsIJAR::VALID)
             { // Compare digests
-              if (storedSectionDigest.Length() == 0)
+              if (storedSectionDigest.IsEmpty())
                 curItemSF->status = nsIJAR::NOT_SIGNED;
               else
               {
diff --git a/mozilla/netwerk/base/src/nsSimpleURI.cpp b/mozilla/netwerk/base/src/nsSimpleURI.cpp
index b8623ec02a4..f555edbab2d 100644
--- a/mozilla/netwerk/base/src/nsSimpleURI.cpp
+++ b/mozilla/netwerk/base/src/nsSimpleURI.cpp
@@ -135,7 +135,7 @@ NS_IMETHODIMP
 nsSimpleURI::SetSpec(const nsACString &aSpec)
 {
     nsCAutoString spec;
-    if (aSpec.Length() == 0) {
+    if (aSpec.IsEmpty()) {
         mScheme.Truncate();
         mPath.Truncate();
         return NS_OK;
diff --git a/mozilla/netwerk/base/src/nsStandardURL.cpp b/mozilla/netwerk/base/src/nsStandardURL.cpp
index 970253c1cf0..9815201da34 100644
--- a/mozilla/netwerk/base/src/nsStandardURL.cpp
+++ b/mozilla/netwerk/base/src/nsStandardURL.cpp
@@ -1505,7 +1505,7 @@ nsStandardURL::Resolve(const nsACString &in, nsACString &out)
     nsCAutoString buf;
     relpath = FilterString(relpath, buf);
     // Calculate the new relpath length if FilterString modified it
-    const PRInt32 relpathLen = buf.Length() != 0 ? 
+    const PRInt32 relpathLen = !buf.IsEmpty() ?
                                buf.Length() : flat.Length();
     // XXX hack hack hack
     char *p = nsnull;
diff --git a/mozilla/netwerk/mime/src/nsMIMEInfoImpl.cpp b/mozilla/netwerk/mime/src/nsMIMEInfoImpl.cpp
index 79f844b53ea..a82d6d9b5a5 100644
--- a/mozilla/netwerk/mime/src/nsMIMEInfoImpl.cpp
+++ b/mozilla/netwerk/mime/src/nsMIMEInfoImpl.cpp
@@ -181,7 +181,7 @@ NS_IMETHODIMP
 nsMIMEInfoImpl::GetMIMEType(char * *aMIMEType) {
     if (!aMIMEType) return NS_ERROR_NULL_POINTER;
 
-    if (mMIMEType.Length() < 1)
+    if (mMIMEType.IsEmpty())
         return NS_ERROR_NOT_INITIALIZED;
 
     *aMIMEType = ToNewCString(mMIMEType);
@@ -266,7 +266,7 @@ NS_IMETHODIMP nsMIMEInfoImpl::SetFileExtensions( const char* aExtensions )
 		mExtensions.AppendCString( ext );
 		extList.Cut(0, breakLocation+1 );
 	}
-	if ( extList.Length() )
+	if ( !extList.IsEmpty() )
 		mExtensions.AppendCString( extList );
 	return NS_OK;
 }
diff --git a/mozilla/netwerk/protocol/keyword/src/nsKeywordProtocolHandler.cpp b/mozilla/netwerk/protocol/keyword/src/nsKeywordProtocolHandler.cpp
index 2232b1ef365..74ea4d10265 100644
--- a/mozilla/netwerk/protocol/keyword/src/nsKeywordProtocolHandler.cpp
+++ b/mozilla/netwerk/protocol/keyword/src/nsKeywordProtocolHandler.cpp
@@ -186,7 +186,7 @@ nsKeywordProtocolHandler::NewChannel(nsIURI* uri, nsIChannel* *result)
 {
     nsresult rv;
 
-    NS_ASSERTION((mKeywordURL.Length() > 0), "someone's trying to use the keyword handler even though it hasn't been init'd");
+    NS_ASSERTION(!mKeywordURL.IsEmpty(), "someone's trying to use the keyword handler even though it hasn't been init'd");
 
     nsCAutoString path;
     rv = uri->GetPath(path);
diff --git a/mozilla/netwerk/test/TestPageLoad.cpp b/mozilla/netwerk/test/TestPageLoad.cpp
index 15050286ff8..c26284b3386 100644
--- a/mozilla/netwerk/test/TestPageLoad.cpp
+++ b/mozilla/netwerk/test/TestPageLoad.cpp
@@ -92,7 +92,7 @@ static NS_METHOD streamParse (nsIInputStream* in,
   int i = 0;
   char *tmp;
 
-  if(globalStream.Length() > 0) {
+  if(!globalStream.IsEmpty()) {
     globalStream.AppendWithConversion(fromRawSegment);
     tmp = ToNewCString(globalStream);
     //printf("\n>>NOW:\n^^^^^\n%s\n^^^^^^^^^^^^^^", tmp);
diff --git a/mozilla/parser/htmlparser/src/nsExpatDriver.cpp b/mozilla/parser/htmlparser/src/nsExpatDriver.cpp
index 5461f7ebc0d..711e426b17e 100644
--- a/mozilla/parser/htmlparser/src/nsExpatDriver.cpp
+++ b/mozilla/parser/htmlparser/src/nsExpatDriver.cpp
@@ -956,7 +956,7 @@ nsExpatDriver::CanParse(CParserContext& aParserContext,
       result=ePrimaryDetect;
     }
     else {
-      if (0 == aParserContext.mMimeType.Length() &&
+      if (aParserContext.mMimeType.IsEmpty() &&
           kNotFound != aBuffer.Find("<?xml ")) {
         aParserContext.SetMimeType(NS_LITERAL_CSTRING(kXMLTextContentType));
         result=eValidDetect;
diff --git a/mozilla/parser/htmlparser/src/nsLoggingSink.cpp b/mozilla/parser/htmlparser/src/nsLoggingSink.cpp
index ced60b94341..31b77588a35 100644
--- a/mozilla/parser/htmlparser/src/nsLoggingSink.cpp
+++ b/mozilla/parser/htmlparser/src/nsLoggingSink.cpp
@@ -609,7 +609,7 @@ nsLoggingSink::WriteAttributes(const nsIParserNode& aNode) {
  
     tmp.Truncate();
     tmp.Append(v);
-    if(tmp.Length() > 0) {
+    if(!tmp.IsEmpty()) {
       PRUnichar first = tmp.First();
       if ((first == '"') || (first == '\'')) {
         if (tmp.Last() == first) {
@@ -669,7 +669,7 @@ nsLoggingSink::WillWriteAttributes(const nsIParserNode& aNode)
     PRInt32 lineNo = 0;
 
     dtd->CollectSkippedContent(aNode.GetNodeType(), content, lineNo);
-    if (content.Length() > 0) {
+    if (!content.IsEmpty()) {
       return PR_TRUE;
     }
   }
@@ -778,7 +778,7 @@ nsLoggingSink::GetNewCString(const nsAString& aValue, char** aResult)
   nsAutoString temp;
   result=QuoteText(aValue,temp);
   if(NS_SUCCEEDED(result)) {
-    if(temp.Length()>0) {
+    if(!temp.IsEmpty()) {
       *aResult = ToNewCString(temp);
     }
   }
diff --git a/mozilla/parser/htmlparser/src/nsParser.cpp b/mozilla/parser/htmlparser/src/nsParser.cpp
index 2075731e705..b55ea8e9364 100644
--- a/mozilla/parser/htmlparser/src/nsParser.cpp
+++ b/mozilla/parser/htmlparser/src/nsParser.cpp
@@ -1567,7 +1567,7 @@ nsParser::Parse(const nsAString& aSourceBuffer,
 
   nsresult result=NS_OK;
 
-  if(aLastCall && (0==aSourceBuffer.Length())) {
+  if(aLastCall && aSourceBuffer.IsEmpty()) {
     // Nothing is being passed to the parser so return
     // immediately. mUnusedInput will get processed when
     // some data is actually passed in.
@@ -1583,7 +1583,7 @@ nsParser::Parse(const nsAString& aSourceBuffer,
   // till we're completely done. 
   nsCOMPtr<nsIParser> kungFuDeathGrip(this);
 
-  if(aSourceBuffer.Length() || mUnusedInput.Length()) { 
+  if(!aSourceBuffer.IsEmpty() || !mUnusedInput.IsEmpty()) {
     
     if (aVerifyEnabled) {
       mFlags |= NS_PARSER_FLAG_DTD_VERIFICATION;
@@ -1747,7 +1747,7 @@ nsresult nsParser::ResumeParse(PRBool allowIteration, PRBool aIsFinalChunk, PRBo
        
       while((result==NS_OK) && (theIterationIsOk)) {
         theFirstTime=PR_FALSE;
-        if(mUnusedInput.Length()>0) {
+        if(!mUnusedInput.IsEmpty()) {
           if(mParserContext->mScanner) {
             // -- Ref: Bug# 22485 --
             // Insert the unused input into the source buffer 
@@ -2163,7 +2163,7 @@ static PRBool DetectByteOrderMark(const unsigned char* aBytes, PRInt32 aLen, nsS
    // }
    // break;
  }  // switch
- return oCharset.Length() > 0;
+ return !oCharset.IsEmpty();
 }
 
 inline const char GetNextChar(nsACString::const_iterator& aStart,
diff --git a/mozilla/profile/pref-migrator/src/nsPrefMigration.cpp b/mozilla/profile/pref-migrator/src/nsPrefMigration.cpp
index 9f7ed62ce44..e61006c9df2 100644
--- a/mozilla/profile/pref-migrator/src/nsPrefMigration.cpp
+++ b/mozilla/profile/pref-migrator/src/nsPrefMigration.cpp
@@ -1906,7 +1906,7 @@ Fix4xCookies(nsIFileSpec * profilePath) {
   while (GetCookieLine(inStream,inBuffer) != -1){
 
     /* skip line if it is a comment or null line */
-    if (inBuffer.Length() == 0 || inBuffer.CharAt(0) == '#' ||
+    if (inBuffer.IsEmpty() || inBuffer.CharAt(0) == '#' ||
         inBuffer.CharAt(0) == nsCRT::CR || inBuffer.CharAt(0) == nsCRT::LF) {
       PutCookieLine(outStream, inBuffer);
       continue;
diff --git a/mozilla/profile/src/nsProfile.cpp b/mozilla/profile/src/nsProfile.cpp
index c0b7525cd95..17ab44233a0 100644
--- a/mozilla/profile/src/nsProfile.cpp
+++ b/mozilla/profile/src/nsProfile.cpp
@@ -459,7 +459,7 @@ nsProfile::LoadDefaultProfileDir(nsCString & profileURLStr, PRBool canInteract)
     
     GetProfileCount(&numProfiles);
 
-    if (profileURLStr.Length() == 0)
+    if (profileURLStr.IsEmpty())
     {
         // If this flag is TRUE, it makes the multiple profile case
         // just like the single profile case - the profile will be
@@ -515,7 +515,7 @@ nsProfile::LoadDefaultProfileDir(nsCString & profileURLStr, PRBool canInteract)
             profileURLStr = PROFILE_SELECTION_URL;
     }
 
-    if (profileURLStr.Length() != 0)
+    if (!profileURLStr.IsEmpty())
     {
         if (!canInteract) return NS_ERROR_PROFILE_REQUIRES_INTERACTION;
 
diff --git a/mozilla/profile/src/nsProfileAccess.cpp b/mozilla/profile/src/nsProfileAccess.cpp
index d21f9e59e0a..d838d35147b 100644
--- a/mozilla/profile/src/nsProfileAccess.cpp
+++ b/mozilla/profile/src/nsProfileAccess.cpp
@@ -1503,7 +1503,7 @@ nsresult ProfileStruct::ExternalizeLocation(nsIRegistry *aRegistry, nsRegistryKe
                                  regData.get());
 
     }
-    else if (regLocationData.Length() != 0)
+    else if (!regLocationData.IsEmpty())
     {
         // Write the original data back out - maybe it can be resolved later.
         rv = aRegistry->SetString(profKey,
diff --git a/mozilla/rdf/chrome/src/nsChromeRegistry.cpp b/mozilla/rdf/chrome/src/nsChromeRegistry.cpp
index da716564b6d..1f1a8cfceea 100644
--- a/mozilla/rdf/chrome/src/nsChromeRegistry.cpp
+++ b/mozilla/rdf/chrome/src/nsChromeRegistry.cpp
@@ -484,7 +484,7 @@ SplitURL(nsIURI *aChromeURI, nsCString& aPackage, nsCString& aProvider, nsCStrin
   aProvider.Right(aFile, aProvider.Length() - (idx + 1));
   aProvider.Truncate(idx);
 
-  PRBool nofile = (aFile.Length() == 0);
+  PRBool nofile = aFile.IsEmpty();
   if (nofile) {
     // If there is no file, then construct the default file
     aFile = aPackage;
diff --git a/mozilla/security/manager/ssl/src/nsOCSPResponder.cpp b/mozilla/security/manager/ssl/src/nsOCSPResponder.cpp
index 47e34a6ae4c..0d32e247d5e 100644
--- a/mozilla/security/manager/ssl/src/nsOCSPResponder.cpp
+++ b/mozilla/security/manager/ssl/src/nsOCSPResponder.cpp
@@ -140,14 +140,14 @@ PRInt32 nsOCSPResponder::CompareEntries(nsIOCSPResponder *a, nsIOCSPResponder *b
   b->GetServiceURL(getter_Copies(bURL));
   bURLAuto.Assign(bURL);
 
-  if (aURLAuto.Length() > 0 ) {
-    if (bURLAuto.Length() > 0) {
+  if (!aURLAuto.IsEmpty()) {
+    if (!bURLAuto.IsEmpty()) {
       return nsOCSPResponder::CmpCAName(a, b);
     } else {
       return -1;
     }
   } else {
-    if (bURLAuto.Length() > 0) {
+    if (!bURLAuto.IsEmpty()) {
       return 1;
     } else {
       return nsOCSPResponder::CmpCAName(a, b);
diff --git a/mozilla/uriloader/exthandler/nsMIMEInfoImpl.cpp b/mozilla/uriloader/exthandler/nsMIMEInfoImpl.cpp
index 79f844b53ea..a82d6d9b5a5 100644
--- a/mozilla/uriloader/exthandler/nsMIMEInfoImpl.cpp
+++ b/mozilla/uriloader/exthandler/nsMIMEInfoImpl.cpp
@@ -181,7 +181,7 @@ NS_IMETHODIMP
 nsMIMEInfoImpl::GetMIMEType(char * *aMIMEType) {
     if (!aMIMEType) return NS_ERROR_NULL_POINTER;
 
-    if (mMIMEType.Length() < 1)
+    if (mMIMEType.IsEmpty())
         return NS_ERROR_NOT_INITIALIZED;
 
     *aMIMEType = ToNewCString(mMIMEType);
@@ -266,7 +266,7 @@ NS_IMETHODIMP nsMIMEInfoImpl::SetFileExtensions( const char* aExtensions )
 		mExtensions.AppendCString( ext );
 		extList.Cut(0, breakLocation+1 );
 	}
-	if ( extList.Length() )
+	if ( !extList.IsEmpty() )
 		mExtensions.AppendCString( extList );
 	return NS_OK;
 }
diff --git a/mozilla/widget/src/beos/nsFilePicker.cpp b/mozilla/widget/src/beos/nsFilePicker.cpp
index 0ebe7991750..acf97e3ef64 100644
--- a/mozilla/widget/src/beos/nsFilePicker.cpp
+++ b/mozilla/widget/src/beos/nsFilePicker.cpp
@@ -112,14 +112,14 @@ NS_IMETHODIMP nsFilePicker::Show(PRInt16 *retval)
 	if (!ppanel) return PR_FALSE;
 
 	// set title
-	if (mTitle.Length() > 0) {
+	if (!mTitle.IsEmpty()) {
 		char *title_utf8 = ToNewUTF8String(mTitle);
 		ppanel->Window()->SetTitle(title_utf8);
 		Recycle(title_utf8);
 	}
 
 	// set default text
-	if (mDefault.Length() > 0) {
+	if (!mDefault.IsEmpty()) {
 		char *defaultText = ToNewUTF8String(mDefault);
 		ppanel->SetSaveText(defaultText);
 		Recycle(defaultText);
@@ -352,7 +352,7 @@ void nsFilePicker::GetFileSystemCharset(nsString & fileSystemCharset)
 	static nsAutoString aCharset;
 	nsresult rv;
 
-	if (aCharset.Length() < 1) {
+	if (aCharset.IsEmpty()) {
 		nsCOMPtr <nsIPlatformCharset> platformCharset = do_GetService(NS_PLATFORMCHARSET_CONTRACTID, &rv);
 		if (NS_SUCCEEDED(rv))
 			rv = platformCharset->GetCharset(kPlatformCharsetSel_FileName, aCharset);
diff --git a/mozilla/widget/src/gtk/nsGtkIMEHelper.cpp b/mozilla/widget/src/gtk/nsGtkIMEHelper.cpp
index afbb70cb2bf..a4414ca00ce 100644
--- a/mozilla/widget/src/gtk/nsGtkIMEHelper.cpp
+++ b/mozilla/widget/src/gtk/nsGtkIMEHelper.cpp
@@ -133,7 +133,7 @@ void nsGtkIMEHelper::SetupUnicodeDecoder()
     nsAutoString charset;
     charset.Assign(NS_LITERAL_STRING(""));
     result = platform->GetCharset(kPlatformCharsetSel_Menu, charset);
-    if (NS_FAILED(result) || (charset.Length() == 0)) {
+    if (NS_FAILED(result) || charset.IsEmpty()) {
       charset.Assign(NS_LITERAL_STRING("ISO-8859-1"));   // default
     }
     nsICharsetConverterManager* manager = nsnull;
diff --git a/mozilla/widget/src/mac/nsMacControl.cpp b/mozilla/widget/src/mac/nsMacControl.cpp
index 3a7341d226e..111d777bdae 100644
--- a/mozilla/widget/src/mac/nsMacControl.cpp
+++ b/mozilla/widget/src/mac/nsMacControl.cpp
@@ -613,7 +613,7 @@ void nsMacControl::GetFileSystemCharset(nsString & fileSystemCharset)
   static nsAutoString aCharset;
   nsresult rv;
 
-  if (aCharset.Length() < 1) {
+  if (aCharset.IsEmpty()) {
     nsCOMPtr <nsIPlatformCharset> platformCharset = do_GetService(NS_PLATFORMCHARSET_CONTRACTID, &rv);
 	  if (NS_SUCCEEDED(rv)) 
 		  rv = platformCharset->GetCharset(kPlatformCharsetSel_FileName, aCharset);
diff --git a/mozilla/xpcom/io/nsLinebreakConverter.cpp b/mozilla/xpcom/io/nsLinebreakConverter.cpp
index 18df7a4526d..a1e471fabdb 100644
--- a/mozilla/xpcom/io/nsLinebreakConverter.cpp
+++ b/mozilla/xpcom/io/nsLinebreakConverter.cpp
@@ -469,7 +469,7 @@ nsresult nsLinebreakConverter::ConvertStringLineBreaks(nsString& ioString,
   NS_ASSERTION(aDestBreaks != eLinebreakAny, "Invalid parameter");
 
   // nothing to do
-  if (ioString.Length() == 0) return NS_OK;
+  if (ioString.IsEmpty()) return NS_OK;
   
   nsresult rv;
   
diff --git a/mozilla/xpcom/io/nsLocalFileOSX.cpp b/mozilla/xpcom/io/nsLocalFileOSX.cpp
index d981f75933b..1954ee14ce4 100644
--- a/mozilla/xpcom/io/nsLocalFileOSX.cpp
+++ b/mozilla/xpcom/io/nsLocalFileOSX.cpp
@@ -1142,7 +1142,7 @@ NS_IMETHODIMP nsLocalFile::InitWithPath(const nsAString& filePath)
 /* [noscript] void initWithNativePath (in ACString filePath); */
 NS_IMETHODIMP nsLocalFile::InitWithNativePath(const nsACString& filePath)
 {
-  if (filePath.First() != '/' || filePath.Length() == 0)
+  if (filePath.IsEmpty() || filePath.First() != '/')
     return NS_ERROR_FILE_UNRECOGNIZED_PATH;
   // On 10.2, huge paths crash CFURLGetFSRef()
   if (filePath.Length() > PATH_MAX)
diff --git a/mozilla/xpfe/appshell/src/nsAppShellWindowEnumerator.cpp b/mozilla/xpfe/appshell/src/nsAppShellWindowEnumerator.cpp
index 21e9aec6494..84bf7e9b26c 100644
--- a/mozilla/xpfe/appshell/src/nsAppShellWindowEnumerator.cpp
+++ b/mozilla/xpfe/appshell/src/nsAppShellWindowEnumerator.cpp
@@ -326,7 +326,7 @@ nsWindowInfo *nsASDOMWindowEarlyToLateEnumerator::FindNext() {
 
   nsWindowInfo *info,
                *listEnd;
-  PRBool        allWindows = mType.Length() == 0;
+  PRBool        allWindows = mType.IsEmpty();
 
   // see nsXULWindowEarlyToLateEnumerator::FindNext
   if (!mCurrentPosition)
@@ -365,7 +365,7 @@ nsWindowInfo *nsASXULWindowEarlyToLateEnumerator::FindNext() {
 
   nsWindowInfo *info,
                *listEnd;
-  PRBool        allWindows = mType.Length() == 0;
+  PRBool        allWindows = mType.IsEmpty();
 
   /* mCurrentPosition null is assumed to mean that the enumerator has run
      its course and is now basically useless. It could also be interpreted
@@ -410,7 +410,7 @@ nsWindowInfo *nsASDOMWindowFrontToBackEnumerator::FindNext() {
 
   nsWindowInfo *info,
                *listEnd;
-  PRBool        allWindows = mType.Length() == 0;
+  PRBool        allWindows = mType.IsEmpty();
 
   // see nsXULWindowEarlyToLateEnumerator::FindNext
   if (!mCurrentPosition)
@@ -450,7 +450,7 @@ nsWindowInfo *nsASXULWindowFrontToBackEnumerator::FindNext() {
 
   nsWindowInfo *info,
                *listEnd;
-  PRBool        allWindows = mType.Length() == 0;
+  PRBool        allWindows = mType.IsEmpty();
 
   // see nsXULWindowEarlyToLateEnumerator::FindNext
   if (!mCurrentPosition)
@@ -490,7 +490,7 @@ nsWindowInfo *nsASDOMWindowBackToFrontEnumerator::FindNext() {
 
   nsWindowInfo *info,
                *listEnd;
-  PRBool        allWindows = mType.Length() == 0;
+  PRBool        allWindows = mType.IsEmpty();
 
   // see nsXULWindowEarlyToLateEnumerator::FindNext
   if (!mCurrentPosition)
@@ -533,7 +533,7 @@ nsWindowInfo *nsASXULWindowBackToFrontEnumerator::FindNext() {
 
   nsWindowInfo *info,
                *listEnd;
-  PRBool        allWindows = mType.Length() == 0;
+  PRBool        allWindows = mType.IsEmpty();
 
   // see nsXULWindowEarlyToLateEnumerator::FindNext
   if (!mCurrentPosition)
diff --git a/mozilla/xpfe/appshell/src/nsChromeTreeOwner.cpp b/mozilla/xpfe/appshell/src/nsChromeTreeOwner.cpp
index 63e42b3f654..12f14de776d 100644
--- a/mozilla/xpfe/appshell/src/nsChromeTreeOwner.cpp
+++ b/mozilla/xpfe/appshell/src/nsChromeTreeOwner.cpp
@@ -116,7 +116,7 @@ NS_IMETHODIMP nsChromeTreeOwner::FindItemWithName(const PRUnichar* aName,
    PRBool fIs_Content = PR_FALSE;
 
    /* Special Cases */
-   if(name.Length() == 0)
+   if(name.IsEmpty())
       return NS_OK;
    if(name.EqualsIgnoreCase("_blank"))
       return NS_OK;
diff --git a/mozilla/xpfe/appshell/src/nsContentTreeOwner.cpp b/mozilla/xpfe/appshell/src/nsContentTreeOwner.cpp
index 2aa5c770523..314d2e05ec1 100644
--- a/mozilla/xpfe/appshell/src/nsContentTreeOwner.cpp
+++ b/mozilla/xpfe/appshell/src/nsContentTreeOwner.cpp
@@ -162,7 +162,7 @@ NS_IMETHODIMP nsContentTreeOwner::FindItemWithName(const PRUnichar* aName,
    PRBool fIs_Content = PR_FALSE;
 
    /* Special Cases */
-   if(name.Length() == 0)
+   if(name.IsEmpty())
       return NS_OK;
    if(name.EqualsIgnoreCase("_blank"))
       return NS_OK;
@@ -603,9 +603,9 @@ NS_IMETHODIMP nsContentTreeOwner::SetTitle(const PRUnichar* aTitle)
    nsAutoString   title;
    nsAutoString   docTitle(aTitle);
 
-   if(docTitle.Length() > 0)
+   if(!docTitle.IsEmpty())
       {
-      if(mTitlePreface.Length() > 0)
+      if(!mTitlePreface.IsEmpty())
          {
          // Title will be: "Preface: Doc Title - Mozilla"
          title.Assign(mTitlePreface);
diff --git a/mozilla/xpfe/appshell/src/nsUserInfoUnix.cpp b/mozilla/xpfe/appshell/src/nsUserInfoUnix.cpp
index 7b3a48c10fb..84d876e8ca6 100644
--- a/mozilla/xpfe/appshell/src/nsUserInfoUnix.cpp
+++ b/mozilla/xpfe/appshell/src/nsUserInfoUnix.cpp
@@ -93,7 +93,7 @@ nsUserInfo::GetFullname(PRUnichar **aFullname)
     // replace ampersand with username
     if (pw->pw_name) {
         nsCAutoString username(pw->pw_name);
-        if (username.Length() > 0 && nsCRT::IsLower(username.CharAt(0)))
+        if (!username.IsEmpty() && nsCRT::IsLower(username.CharAt(0)))
             username.SetCharAt(nsCRT::ToUpper(username.CharAt(0)), 0);
             
         fullname.ReplaceSubstring("&", username.get());
diff --git a/mozilla/xpfe/appshell/src/nsWebShellWindow.cpp b/mozilla/xpfe/appshell/src/nsWebShellWindow.cpp
index bbbbab3a721..cfc73323116 100644
--- a/mozilla/xpfe/appshell/src/nsWebShellWindow.cpp
+++ b/mozilla/xpfe/appshell/src/nsWebShellWindow.cpp
@@ -1422,7 +1422,7 @@ void nsWebShellWindow::LoadContentAreas() {
 
   // content URLs are specified in the search part of the URL
   // as <contentareaID>=<escapedURL>[;(repeat)]
-  if (searchSpec.Length() > 0) {
+  if (!searchSpec.IsEmpty()) {
     PRInt32     begPos,
                 eqPos,
                 endPos;
diff --git a/mozilla/xpfe/appshell/src/nsWindowMediator.cpp b/mozilla/xpfe/appshell/src/nsWindowMediator.cpp
index 59540aa1410..efd94e61ed0 100644
--- a/mozilla/xpfe/appshell/src/nsWindowMediator.cpp
+++ b/mozilla/xpfe/appshell/src/nsWindowMediator.cpp
@@ -335,7 +335,7 @@ nsWindowMediator::MostRecentWindowInfo(const PRUnichar* inType)
 {
   PRInt32       lastTimeStamp = -1;
   nsAutoString  typeString(inType);
-  PRBool        allWindows = !inType || typeString.Length() == 0;
+  PRBool        allWindows = !inType || typeString.IsEmpty();
 
   // Find the most window with the highest time stamp that matches
   // the requested type
diff --git a/mozilla/xpfe/components/history/src/nsGlobalHistory.cpp b/mozilla/xpfe/components/history/src/nsGlobalHistory.cpp
index 9f08dd0710a..0bcf6447b7e 100644
--- a/mozilla/xpfe/components/history/src/nsGlobalHistory.cpp
+++ b/mozilla/xpfe/components/history/src/nsGlobalHistory.cpp
@@ -3940,7 +3940,7 @@ nsGlobalHistory::OnStartLookup(const PRUnichar *searchString,
   // there is no need to proceed with the search
   nsAutoString cut(searchString);
   AutoCompleteCutPrefix(cut, nsnull);
-  if (cut.Length() == 0) {
+  if (cut.IsEmpty()) {
     listener->OnAutoComplete(results, status);
     return NS_OK;
   }
diff --git a/mozilla/xpfe/components/related/src/nsRelatedLinksHandler.cpp b/mozilla/xpfe/components/related/src/nsRelatedLinksHandler.cpp
index c91b3d87bbf..713be18e650 100644
--- a/mozilla/xpfe/components/related/src/nsRelatedLinksHandler.cpp
+++ b/mozilla/xpfe/components/related/src/nsRelatedLinksHandler.cpp
@@ -385,7 +385,7 @@ RelatedLinksStreamListener::OnDataAvailable(nsIRequest *request, nsISupports *ct
 			mBuffer.Left(oneLiner, eol);
 			mBuffer.Cut(0, eol+1);
 		}
-		if (oneLiner.Length() < 1)	break;
+		if (oneLiner.IsEmpty())	break;
 
 #if 0
 		printf("RL: '%s'\n", NS_LossyConvertUCS2toASCII(oneLiner).get());
@@ -458,7 +458,7 @@ RelatedLinksStreamListener::OnDataAvailable(nsIRequest *request, nsISupports *ct
 				if (NS_SUCCEEDED(rv = gRDFService->GetAnonymousResource(getter_AddRefs(newTopic))))
 				{
 					mDataSource->Assert(newTopic, kRDF_type, kNC_RelatedLinksTopic, PR_TRUE);
-					if (title.Length() > 0)
+					if (!title.IsEmpty())
 					{
                         Unescape(title);
 
@@ -497,7 +497,7 @@ RelatedLinksStreamListener::OnDataAvailable(nsIRequest *request, nsISupports *ct
 			}
 		}
 
-		if (child.Length() > 0)
+		if (!child.IsEmpty())
 		{
 
 #if 0
@@ -511,7 +511,7 @@ RelatedLinksStreamListener::OnDataAvailable(nsIRequest *request, nsISupports *ct
 				if (NS_SUCCEEDED(rv))
 				{
 					title.Trim(" ");
-					if (title.Length() > 0)
+					if (!title.IsEmpty())
 					{
                         Unescape(title);
 
diff --git a/mozilla/xpfe/components/search/src/nsInternetSearchService.cpp b/mozilla/xpfe/components/search/src/nsInternetSearchService.cpp
index b7803484684..367ce2c43fb 100755
--- a/mozilla/xpfe/components/search/src/nsInternetSearchService.cpp
+++ b/mozilla/xpfe/components/search/src/nsInternetSearchService.cpp
@@ -719,7 +719,7 @@ InternetSearchDataSource::FireTimer(nsITimer* aTimer, void* aClosure)
 		if (NS_FAILED(rv = search->GetSearchEngineToPing(getter_AddRefs(searchURI), updateURL)))
 			return;
 		if (!searchURI)			return;
-		if (updateURL.Length() < 1)	return;
+		if (updateURL.IsEmpty())	return;
 
 		search->busyResource = searchURI;
 
@@ -2443,7 +2443,7 @@ InternetSearchDataSource::saveContents(nsIChannel* channel, nsIInternetSearchCon
 	PRInt32			slashOffset = baseName.RFindChar(PRUnichar('/'));
 	if (slashOffset < 0)		return(NS_ERROR_UNEXPECTED);
 	baseName.Cut(0, slashOffset+1);
-	if (baseName.Length() < 1)	return(NS_ERROR_UNEXPECTED);
+	if (baseName.IsEmpty())	return(NS_ERROR_UNEXPECTED);
 
 	// make sure that search engines are .src files
 	PRInt32	extensionOffset;
@@ -2579,7 +2579,7 @@ InternetSearchDataSource::GetInternetSearchURL(const char *searchEngineURI,
 		MapEncoding(encodingStr, queryEncodingStr);
 	}
 
-	if (queryEncodingStr.Length() > 0)
+	if (!queryEncodingStr.IsEmpty())
 	{
  		// remember query charset string
  		mQueryEncodingStr = queryEncodingStr;
@@ -2618,7 +2618,7 @@ InternetSearchDataSource::GetInternetSearchURL(const char *searchEngineURI,
 	    return(rv);
 	if (NS_FAILED(rv = GetInputs(dataUni, userVar, text, input, direction, pageNumber, whichButtons)))
 	    return(rv);
-	if (input.Length() < 1)				return(NS_ERROR_UNEXPECTED);
+	if (input.IsEmpty())				return(NS_ERROR_UNEXPECTED);
 
 	// we can only handle HTTP GET
 	if (!method.EqualsIgnoreCase("get"))	return(NS_ERROR_UNEXPECTED);
@@ -2749,7 +2749,7 @@ InternetSearchDataSource::FindInternetSearchResults(const char *url, PRBool *sea
 		// look for query option which is the string the user is searching for
 		nsAutoString	userVar, inputUnused;
     if (NS_FAILED(rv = GetInputs(dataUni, userVar, nsAutoString(), inputUnused, 0, 0, 0)))  return(rv);
-		if (userVar.Length() < 1)	return(NS_RDF_NO_VALUE);
+		if (userVar.IsEmpty())	return(NS_RDF_NO_VALUE);
 
 		nsAutoString	queryStr;
 		queryStr = NS_LITERAL_STRING("?") +
@@ -2776,7 +2776,7 @@ InternetSearchDataSource::FindInternetSearchResults(const char *url, PRBool *sea
 				searchText.Truncate(andOffset);
 			}
 		}
-		if (searchText.Length() > 0)
+		if (!searchText.IsEmpty())
 		{
  			// apply charset conversion to the search text
  			if (!mQueryEncodingStr.IsEmpty())
@@ -2845,7 +2845,7 @@ InternetSearchDataSource::FindInternetSearchResults(const char *url, PRBool *sea
 		if (NS_SUCCEEDED(rv = mInner->GetTarget(kNC_LastSearchRoot, kNC_Ref, PR_TRUE,
 			getter_AddRefs(oldNode))))
 		{
-			if (engineURI.Length() > 0)
+			if (!engineURI.IsEmpty())
 			{
 				const PRUnichar	*uriUni = engineURI.get();
 				nsCOMPtr<nsIRDFLiteral>	uriLiteral;
@@ -3113,7 +3113,7 @@ InternetSearchDataSource::BeginSearchRequest(nsIRDFResource *source, PRBool doNe
 
 	// parse up attributes
 
-	while(uri.Length() > 0)
+	while(!uri.IsEmpty())
 	{
 		nsAutoString	item;
 
@@ -3137,7 +3137,7 @@ InternetSearchDataSource::BeginSearchRequest(nsIRDFResource *source, PRBool doNe
 		value = item;
 		value.Cut(0, equalOffset + 1);
 		
-		if ((attrib.Length() > 0) && (value.Length() > 0))
+		if (!attrib.IsEmpty() && !value.IsEmpty())
 		{
 			if (attrib.EqualsIgnoreCase("engine"))
 			{
@@ -3276,7 +3276,7 @@ InternetSearchDataSource::FindData(nsIRDFResource *engine, nsIRDFLiteral **dataL
 	}
 
 	// save file contents
-	if (data.Length() < 1)	return(NS_ERROR_UNEXPECTED);
+	if (data.IsEmpty())	return(NS_ERROR_UNEXPECTED);
 
 	rv = updateDataHintsInGraph(engine, data.get());
 
@@ -3448,7 +3448,7 @@ InternetSearchDataSource::updateDataHintsInGraph(nsIRDFResource *engine, const P
 		nsAutoString	updateStr, updateIconStr, updateCheckDaysStr;
 
 		GetData(dataUni, "browser", 0, "update", updateStr);
-		if (updateStr.Length() < 1)
+		if (updateStr.IsEmpty())
 		{
 			// fallback to trying "search"|"updateCheckDays"
 			GetData(dataUni, "search", 0, "update", updateStr);
@@ -3474,17 +3474,17 @@ InternetSearchDataSource::updateDataHintsInGraph(nsIRDFResource *engine, const P
 			// note: its OK if the "updateIcon" isn't specified
 			GetData(dataUni, "browser", 0, "updateIcon", updateIconStr);
 		}
-		if (updateStr.Length() > 0)
+		if (!updateStr.IsEmpty())
 		{
 			GetData(dataUni, "browser", 0, "updateCheckDays", updateCheckDaysStr);
-			if (updateCheckDaysStr.Length() < 1)
+			if (updateCheckDaysStr.IsEmpty())
 			{
 				// fallback to trying "search"|"updateCheckDays"
 				GetData(dataUni, "search", 0, "updateCheckDays", updateCheckDaysStr);
 			}
 		}
 
-		if ((updateStr.Length() > 0) && (updateCheckDaysStr.Length() > 0))
+		if (!updateStr.IsEmpty() && !updateCheckDaysStr.IsEmpty())
 		{
 			nsCOMPtr<nsIRDFLiteral>	updateLiteral;
 			if (NS_SUCCEEDED(rv = gRDFService->GetLiteral(updateStr.get(),
@@ -3508,7 +3508,7 @@ InternetSearchDataSource::updateDataHintsInGraph(nsIRDFResource *engine, const P
 				rv = updateAtom(mInner, engine, kNC_UpdateCheckDays, updateCheckDaysLiteral, nsnull);
 			}
 
-			if (updateIconStr.Length() > 0)
+			if (!updateIconStr.IsEmpty())
 			{
 				nsCOMPtr<nsIRDFLiteral>	updateIconLiteral;
 				if (NS_SUCCEEDED(rv = gRDFService->GetLiteral(updateIconStr.get(),
@@ -3828,7 +3828,7 @@ InternetSearchDataSource::DoSearch(nsIRDFResource *source, nsIRDFResource *engin
 	dataLit->GetValueConst(&dataUni);
 	if (!dataUni)			return(NS_RDF_NO_VALUE);
 
-	if (fullURL.Length() > 0)
+	if (!fullURL.IsEmpty())
 	{
 		action.Assign(fullURL);
 		methodStr.Assign(NS_LITERAL_STRING("get"));
@@ -3844,14 +3844,14 @@ InternetSearchDataSource::DoSearch(nsIRDFResource *source, nsIRDFResource *engin
 	// first look for "interpret/charset"... if that isn't specified,
 	// then fall back to looking for "interpret/resultEncoding" (a decimal)
 	GetData(dataUni, "interpret", 0, "charset", resultEncodingStr);
-	if (resultEncodingStr.Length() < 1)
+	if (resultEncodingStr.IsEmpty())
 	{
 		GetData(dataUni, "interpret", 0, "resultEncoding", encodingStr);	// decimal string values
 		MapEncoding(encodingStr, resultEncodingStr);
 	}
 	// rjc note: ignore "interpret/resultTranslationEncoding" as well as
 	// "interpret/resultTranslationFont" since we always convert results to Unicode
-	if (resultEncodingStr.Length() > 0)
+	if (!resultEncodingStr.IsEmpty())
 	{
 		nsCOMPtr <nsICharsetConverterManager2> charsetConv = do_GetService(NS_CHARSETCONVERTERMANAGER_CONTRACTID, &rv);
 		if (NS_SUCCEEDED(rv))
@@ -3871,12 +3871,12 @@ InternetSearchDataSource::DoSearch(nsIRDFResource *source, nsIRDFResource *engin
 	// then fall back to looking for "search/queryEncoding" (a decimal)
 	nsAutoString    queryEncodingStr;
 	GetData(dataUni, "search", 0, "queryCharset", queryEncodingStr);
-	if (queryEncodingStr.Length() < 1)
+	if (queryEncodingStr.IsEmpty())
 	{
 		GetData(dataUni, "search", 0, "queryEncoding", encodingStr);		// decimal string values
 		MapEncoding(encodingStr, queryEncodingStr);
 	}
-	if (queryEncodingStr.Length() > 0)
+	if (!queryEncodingStr.IsEmpty())
 	{
 		// convert from escaped-UTF_8, to unicode, and then to
 		// the charset indicated by the dataset in question
@@ -3907,13 +3907,10 @@ InternetSearchDataSource::DoSearch(nsIRDFResource *source, nsIRDFResource *engin
 		}
 	}
 
-	if (fullURL.Length() > 0)
-	{
-	}
-	else if (methodStr.EqualsIgnoreCase("get"))
+	if (fullURL.IsEmpty() && methodStr.EqualsIgnoreCase("get"))
 	{
     if (NS_FAILED(rv = GetInputs(dataUni, userVar, textTemp, input, 0, 0, 0)))  return(rv);
-		if (input.Length() < 1)				return(NS_ERROR_UNEXPECTED);
+		if (input.IsEmpty())				return(NS_ERROR_UNEXPECTED);
 
 		// HTTP Get method support
 		action += NS_LITERAL_STRING("?") + input;
@@ -4412,7 +4409,7 @@ InternetSearchDataSource::GetNumInterpretSections(const PRUnichar *dataUni, PRUi
 	NS_NAMED_LITERAL_STRING(section, "<interpret");
 	PRBool		inSection = PR_FALSE;
 
-	while(buffer.Length() > 0)
+	while(!buffer.IsEmpty())
 	{
 		PRInt32 eol = buffer.FindCharInSet("\r\n", 0);
 		if (eol < 0)	break;
@@ -4422,7 +4419,7 @@ InternetSearchDataSource::GetNumInterpretSections(const PRUnichar *dataUni, PRUi
 			buffer.Left(line, eol);
 		}
 		buffer.Cut(0, eol+1);
-		if (line.Length() < 1)	continue;		// skip empty lines
+		if (line.IsEmpty())	continue;		// skip empty lines
 		if (line[0] == PRUnichar('#'))	continue;	// skip comments
 		line.Trim(" \t");
 		if (inSection == PR_FALSE)
@@ -4461,7 +4458,7 @@ InternetSearchDataSource::GetData(const PRUnichar *dataUni, const char *sectionT
 	section.Assign(NS_LITERAL_STRING("<"));
 	section.AppendWithConversion(sectionToFind);
 
-	while(buffer.Length() > 0)
+	while(!buffer.IsEmpty())
 	{
 		PRInt32 eol = buffer.FindCharInSet("\r\n", 0);
 		if (eol < 0)	break;
@@ -4471,7 +4468,7 @@ InternetSearchDataSource::GetData(const PRUnichar *dataUni, const char *sectionT
 			buffer.Left(line, eol);
 		}
 		buffer.Cut(0, eol+1);
-		if (line.Length() < 1)	continue;		// skip empty lines
+		if (line.IsEmpty())	continue;		// skip empty lines
 		if (line[0] == PRUnichar('#'))	continue;	// skip comments
 		line.Trim(" \t");
 		if (inSection == PR_FALSE)
@@ -4516,7 +4513,7 @@ InternetSearchDataSource::GetData(const PRUnichar *dataUni, const char *sectionT
 			{
 				PRUnichar quoteChar = value[0];
 				value.Cut(0,1);
-				if (value.Length() > 0)
+				if (!value.IsEmpty())
 				{
 					PRInt32 quoteEnd = value.FindChar(quoteChar);
 					if (quoteEnd >= 0)
@@ -4553,7 +4550,7 @@ InternetSearchDataSource::GetInputs(const PRUnichar *dataUni, nsString &userVar,
 	PRBool		inSection = PR_FALSE;
   PRBool        inDirInput; // directional input: "inputnext" or "inputprev"
 
-	while(buffer.Length() > 0)
+	while(!buffer.IsEmpty())
 	{
 		PRInt32 eol = buffer.FindCharInSet("\r\n", 0);
 		if (eol < 0)	break;
@@ -4563,7 +4560,7 @@ InternetSearchDataSource::GetInputs(const PRUnichar *dataUni, nsString &userVar,
 			buffer.Left(line, eol);
 		}
 		buffer.Cut(0, eol+1);
-		if (line.Length() < 1)	continue;		// skip empty lines
+		if (line.IsEmpty())	continue;		// skip empty lines
 		if (line[0] == PRUnichar('#'))	continue;	// skip comments
 		line.Trim(" \t");
 		if (inSection == PR_FALSE)
@@ -4647,7 +4644,7 @@ InternetSearchDataSource::GetInputs(const PRUnichar *dataUni, nsString &userVar,
 					}
 				}
 			}
-			if (nameAttrib.Length() <= 0)	continue;
+			if (nameAttrib.IsEmpty())	continue;
 
 			// first look for value attribute
 			nsAutoString	valueAttrib;
@@ -4696,9 +4693,9 @@ InternetSearchDataSource::GetInputs(const PRUnichar *dataUni, nsString &userVar,
 			if (line.RFind("mode=browser", PR_TRUE) >= 0)
 				continue;
 
-			if ((nameAttrib.Length() > 0) && (valueAttrib.Length() > 0))
+			if (!nameAttrib.IsEmpty() && !valueAttrib.IsEmpty())
 			{
-				if (input.Length() > 0)
+				if (!input.IsEmpty())
 				{
 					input.Append(NS_LITERAL_STRING("&"));
 				}
@@ -4937,7 +4934,7 @@ InternetSearchDataSource::OnStopRequest(nsIRequest *request, nsISupports *ctxt,
 		// save out new search engine state data into localstore
 		PRBool			tempDirty = PR_FALSE;
 		nsCOMPtr<nsIRDFLiteral>	newValue;
-		if (lastModValue.Length() > 0)
+		if (!lastModValue.IsEmpty())
 		{
 			gRDFService->GetLiteral(NS_ConvertASCIItoUCS2(lastModValue).get(),
 				getter_AddRefs(newValue));
@@ -4948,7 +4945,7 @@ InternetSearchDataSource::OnStopRequest(nsIRequest *request, nsISupports *ctxt,
 				if (tempDirty == PR_TRUE)	updateSearchEngineFile = PR_TRUE;
 			}
 		}
-		if (contentLengthValue.Length() > 0)
+		if (!contentLengthValue.IsEmpty())
 		{
 			gRDFService->GetLiteral(NS_ConvertASCIItoUCS2(contentLengthValue).get(),
 				getter_AddRefs(newValue));
diff --git a/mozilla/xpfe/components/startup/src/nsUserInfoUnix.cpp b/mozilla/xpfe/components/startup/src/nsUserInfoUnix.cpp
index 7b3a48c10fb..84d876e8ca6 100644
--- a/mozilla/xpfe/components/startup/src/nsUserInfoUnix.cpp
+++ b/mozilla/xpfe/components/startup/src/nsUserInfoUnix.cpp
@@ -93,7 +93,7 @@ nsUserInfo::GetFullname(PRUnichar **aFullname)
     // replace ampersand with username
     if (pw->pw_name) {
         nsCAutoString username(pw->pw_name);
-        if (username.Length() > 0 && nsCRT::IsLower(username.CharAt(0)))
+        if (!username.IsEmpty() && nsCRT::IsLower(username.CharAt(0)))
             username.SetCharAt(nsCRT::ToUpper(username.CharAt(0)), 0);
             
         fullname.ReplaceSubstring("&", username.get());
diff --git a/mozilla/xpinstall/src/nsInstall.cpp b/mozilla/xpinstall/src/nsInstall.cpp
index 33027cc7bf2..b616154b45d 100644
--- a/mozilla/xpinstall/src/nsInstall.cpp
+++ b/mozilla/xpinstall/src/nsInstall.cpp
@@ -2443,7 +2443,7 @@ nsInstall::CurrentUserNode(nsString& userRegNode)
 PRBool
 nsInstall::BadRegName(const nsString& regName)
 {
-    if ( regName.Length() == 0 )
+    if ( regName.IsEmpty() )
         return PR_TRUE;
 
     if ((regName.First() == ' ' ) || (regName.Last() == ' ' ))
diff --git a/mozilla/xpinstall/src/nsJSFile.cpp b/mozilla/xpinstall/src/nsJSFile.cpp
index c4484238a31..384e8ad3f09 100644
--- a/mozilla/xpinstall/src/nsJSFile.cpp
+++ b/mozilla/xpinstall/src/nsJSFile.cpp
@@ -1116,7 +1116,7 @@ InstallFileOpFileWindowsGetShortName(JSContext *cx, JSObject *obj, uintN argc, j
     return JS_TRUE;
   }
 
-  if(shortPathName.Length() != 0)
+  if(!shortPathName.IsEmpty())
     *rval = STRING_TO_JSVAL(JS_NewUCStringCopyN(cx, NS_REINTERPRET_CAST(const jschar*, shortPathName.get()), shortPathName.Length()));
 
   return JS_TRUE;