diff --git a/mozilla/content/html/style/src/nsCSSStyleSheet.cpp b/mozilla/content/html/style/src/nsCSSStyleSheet.cpp
index 472bf6e7372..b0fce35d38c 100644
--- a/mozilla/content/html/style/src/nsCSSStyleSheet.cpp
+++ b/mozilla/content/html/style/src/nsCSSStyleSheet.cpp
@@ -220,7 +220,7 @@ PRInt32 CSSStyleSheetImpl::RulesMatching(nsIPresContext* aPresContext,
     child = ((CSSStyleSheetImpl*)child)->mNext;
   }
 
-  PRInt32 count = ((nsnull != mRules) ? mRules->Count() : 0);
+  PRInt32 count = (mRules.IsNotNull() ? mRules->Count() : 0);
 
   for (PRInt32 index = 0; index < count; index++) {
     nsICSSStyleRulePtr rule = (nsICSSStyleRule*)mRules->ElementAt(index);
@@ -272,12 +272,12 @@ void CSSStyleSheetImpl::AppendStyleSheet(nsICSSStyleSheet* aSheet)
 {
   NS_PRECONDITION(nsnull != aSheet, "null arg");
 
-  if (nsnull == mFirstChild) {
+  if (mFirstChild.IsNull()) {
     mFirstChild.SetAddRef(aSheet);
   }
   else {
     nsICSSStyleSheet* child = mFirstChild;
-    while (nsnull != ((CSSStyleSheetImpl*)child)->mNext) {
+    while (((CSSStyleSheetImpl*)child)->mNext.IsNotNull()) {
       child = ((CSSStyleSheetImpl*)child)->mNext;
     }
     ((CSSStyleSheetImpl*)child)->mNext.SetAddRef(aSheet);
@@ -289,7 +289,7 @@ void CSSStyleSheetImpl::PrependStyleRule(nsICSSStyleRule* aRule)
   NS_PRECONDITION(nsnull != aRule, "null arg");
   //XXX replace this with a binary search?
   PRInt32 weight = aRule->GetWeight();
-  if (nsnull == mRules) {
+  if (mRules.IsNull()) {
     if (NS_OK != NS_NewISupportsArray(mRules.AssignPtr()))
       return;
   }
@@ -309,7 +309,7 @@ void CSSStyleSheetImpl::AppendStyleRule(nsICSSStyleRule* aRule)
 
   //XXX replace this with a binary search?
   PRInt32 weight = aRule->GetWeight();
-  if (nsnull == mRules) {
+  if (mRules.IsNull()) {
     if (NS_OK != NS_NewISupportsArray(mRules.AssignPtr()))
       return;
   }
@@ -343,7 +343,7 @@ void CSSStyleSheetImpl::List(FILE* out, PRInt32 aIndent) const
     child = ((CSSStyleSheetImpl*)child)->mNext;
   }
 
-  PRInt32 count = ((nsnull != mRules) ? mRules->Count() : 0);
+  PRInt32 count = (mRules.IsNotNull() ? mRules->Count() : 0);
 
   for (index = 0; index < count; index++) {
     nsICSSStyleRulePtr rule = (nsICSSStyleRule*)mRules->ElementAt(index);
diff --git a/mozilla/layout/base/nsPresContext.cpp b/mozilla/layout/base/nsPresContext.cpp
index ef54a55f0d0..191aae3eed0 100644
--- a/mozilla/layout/base/nsPresContext.cpp
+++ b/mozilla/layout/base/nsPresContext.cpp
@@ -36,6 +36,7 @@
 
 static NS_DEFINE_IID(kIPresContextIID, NS_IPRESCONTEXT_IID);
 
+#if 0
 // XXX this code needs to move far away from here
 static nsIImageManager* gImageManager = nsnull;
 static void InitImageLibrary()
@@ -50,8 +51,9 @@ static void InitImageLibrary()
   printf("can't initialize image library\n");
 }
 // XXX end code with no home...
+#endif
 
-class ImageLoader :  nsIImageRequestObserver {
+class ImageLoader :  public nsIImageRequestObserver {
 public:
   ImageLoader(nsPresContext* aCX, nsIImageGroup* aGroup, nsIFrame* aFrame);
   ~ImageLoader();
diff --git a/mozilla/layout/base/src/nsPresContext.cpp b/mozilla/layout/base/src/nsPresContext.cpp
index ef54a55f0d0..191aae3eed0 100644
--- a/mozilla/layout/base/src/nsPresContext.cpp
+++ b/mozilla/layout/base/src/nsPresContext.cpp
@@ -36,6 +36,7 @@
 
 static NS_DEFINE_IID(kIPresContextIID, NS_IPRESCONTEXT_IID);
 
+#if 0
 // XXX this code needs to move far away from here
 static nsIImageManager* gImageManager = nsnull;
 static void InitImageLibrary()
@@ -50,8 +51,9 @@ static void InitImageLibrary()
   printf("can't initialize image library\n");
 }
 // XXX end code with no home...
+#endif
 
-class ImageLoader :  nsIImageRequestObserver {
+class ImageLoader :  public nsIImageRequestObserver {
 public:
   ImageLoader(nsPresContext* aCX, nsIImageGroup* aGroup, nsIFrame* aFrame);
   ~ImageLoader();
diff --git a/mozilla/layout/base/src/nsReflowCommand.cpp b/mozilla/layout/base/src/nsReflowCommand.cpp
index 4e04fcfc0c9..34a72cb37c4 100644
--- a/mozilla/layout/base/src/nsReflowCommand.cpp
+++ b/mozilla/layout/base/src/nsReflowCommand.cpp
@@ -237,5 +237,5 @@ nsIFrame* nsReflowCommand::GetNext() const
   if (count > 0) {
     rv = (nsIFrame*) mPath[count - 1];
   }
-  return nsnull;
+  return rv;
 }
diff --git a/mozilla/layout/generic/nsBlockFrame.cpp b/mozilla/layout/generic/nsBlockFrame.cpp
index 84fd53b081b..841c30aa686 100644
--- a/mozilla/layout/generic/nsBlockFrame.cpp
+++ b/mozilla/layout/generic/nsBlockFrame.cpp
@@ -1162,7 +1162,6 @@ nsBlockFrame::ReflowMappedChildren(nsIPresContext* aCX,
 
   PRBool result = PR_TRUE;
   nsIFrame* kidFrame;
-  nsIFrame* prevKidFrame = nsnull;
 
   for (kidFrame = mFirstChild; nsnull != kidFrame; ) {
     nsIContentPtr kid;
@@ -1218,7 +1217,6 @@ nsBlockFrame::ReflowMappedChildren(nsIPresContext* aCX,
     }
 
     // Get the next child frame
-    prevKidFrame = kidFrame;
     kidFrame->GetNextSibling(kidFrame);
   }
 
@@ -1255,7 +1253,7 @@ PRBool nsBlockFrame::MoreToReflow(nsIPresContext* aCX)
     // Get the next content object that we would like to reflow
     PRInt32 kidIndex = NextChildOffset();
     nsIContentPtr kid = mContent->ChildAt(kidIndex);
-    if (nsnull != kid) {
+    if (kid.IsNotNull()) {
       // Resolve style for the kid
       nsIStyleContextPtr kidSC = aCX->ResolveStyleContextFor(kid, this);
       nsStyleDisplay* kidStyleDisplay = (nsStyleDisplay*)
@@ -1318,7 +1316,7 @@ nsBlockFrame::ReflowAppendedChildren(nsIPresContext* aCX,
   for (;;) {
     // Get the next content object
     nsIContentPtr kid = mContent->ChildAt(kidIndex);
-    if (nsnull == kid) {
+    if (kid.IsNull()) {
       result = frComplete;
       break;
     }
@@ -1340,7 +1338,6 @@ nsBlockFrame::ReflowAppendedChildren(nsIPresContext* aCX,
     } else if (nsnull == kidPrevInFlow) {
       // Create initial frame for the child
       nsIContentDelegate* kidDel;
-      nsresult fr;
       switch (kidDisplay->mDisplay) {
       case NS_STYLE_DISPLAY_BLOCK:
       case NS_STYLE_DISPLAY_LIST_ITEM:
@@ -1369,7 +1366,7 @@ nsBlockFrame::ReflowAppendedChildren(nsIPresContext* aCX,
 
       default:
         NS_ASSERTION(nsnull == kidPrevInFlow, "bad prev in flow");
-        fr = nsFrame::NewFrame(&kidFrame, kid, kidIndex, this);
+        nsFrame::NewFrame(&kidFrame, kid, kidIndex, this);
         break;
       }
       kidFrame->SetStyleContext(kidSC);
diff --git a/mozilla/layout/generic/nsBlockReflowState.cpp b/mozilla/layout/generic/nsBlockReflowState.cpp
index 84fd53b081b..841c30aa686 100644
--- a/mozilla/layout/generic/nsBlockReflowState.cpp
+++ b/mozilla/layout/generic/nsBlockReflowState.cpp
@@ -1162,7 +1162,6 @@ nsBlockFrame::ReflowMappedChildren(nsIPresContext* aCX,
 
   PRBool result = PR_TRUE;
   nsIFrame* kidFrame;
-  nsIFrame* prevKidFrame = nsnull;
 
   for (kidFrame = mFirstChild; nsnull != kidFrame; ) {
     nsIContentPtr kid;
@@ -1218,7 +1217,6 @@ nsBlockFrame::ReflowMappedChildren(nsIPresContext* aCX,
     }
 
     // Get the next child frame
-    prevKidFrame = kidFrame;
     kidFrame->GetNextSibling(kidFrame);
   }
 
@@ -1255,7 +1253,7 @@ PRBool nsBlockFrame::MoreToReflow(nsIPresContext* aCX)
     // Get the next content object that we would like to reflow
     PRInt32 kidIndex = NextChildOffset();
     nsIContentPtr kid = mContent->ChildAt(kidIndex);
-    if (nsnull != kid) {
+    if (kid.IsNotNull()) {
       // Resolve style for the kid
       nsIStyleContextPtr kidSC = aCX->ResolveStyleContextFor(kid, this);
       nsStyleDisplay* kidStyleDisplay = (nsStyleDisplay*)
@@ -1318,7 +1316,7 @@ nsBlockFrame::ReflowAppendedChildren(nsIPresContext* aCX,
   for (;;) {
     // Get the next content object
     nsIContentPtr kid = mContent->ChildAt(kidIndex);
-    if (nsnull == kid) {
+    if (kid.IsNull()) {
       result = frComplete;
       break;
     }
@@ -1340,7 +1338,6 @@ nsBlockFrame::ReflowAppendedChildren(nsIPresContext* aCX,
     } else if (nsnull == kidPrevInFlow) {
       // Create initial frame for the child
       nsIContentDelegate* kidDel;
-      nsresult fr;
       switch (kidDisplay->mDisplay) {
       case NS_STYLE_DISPLAY_BLOCK:
       case NS_STYLE_DISPLAY_LIST_ITEM:
@@ -1369,7 +1366,7 @@ nsBlockFrame::ReflowAppendedChildren(nsIPresContext* aCX,
 
       default:
         NS_ASSERTION(nsnull == kidPrevInFlow, "bad prev in flow");
-        fr = nsFrame::NewFrame(&kidFrame, kid, kidIndex, this);
+        nsFrame::NewFrame(&kidFrame, kid, kidIndex, this);
         break;
       }
       kidFrame->SetStyleContext(kidSC);
diff --git a/mozilla/layout/generic/nsBlockReflowState.h b/mozilla/layout/generic/nsBlockReflowState.h
index 84fd53b081b..841c30aa686 100644
--- a/mozilla/layout/generic/nsBlockReflowState.h
+++ b/mozilla/layout/generic/nsBlockReflowState.h
@@ -1162,7 +1162,6 @@ nsBlockFrame::ReflowMappedChildren(nsIPresContext* aCX,
 
   PRBool result = PR_TRUE;
   nsIFrame* kidFrame;
-  nsIFrame* prevKidFrame = nsnull;
 
   for (kidFrame = mFirstChild; nsnull != kidFrame; ) {
     nsIContentPtr kid;
@@ -1218,7 +1217,6 @@ nsBlockFrame::ReflowMappedChildren(nsIPresContext* aCX,
     }
 
     // Get the next child frame
-    prevKidFrame = kidFrame;
     kidFrame->GetNextSibling(kidFrame);
   }
 
@@ -1255,7 +1253,7 @@ PRBool nsBlockFrame::MoreToReflow(nsIPresContext* aCX)
     // Get the next content object that we would like to reflow
     PRInt32 kidIndex = NextChildOffset();
     nsIContentPtr kid = mContent->ChildAt(kidIndex);
-    if (nsnull != kid) {
+    if (kid.IsNotNull()) {
       // Resolve style for the kid
       nsIStyleContextPtr kidSC = aCX->ResolveStyleContextFor(kid, this);
       nsStyleDisplay* kidStyleDisplay = (nsStyleDisplay*)
@@ -1318,7 +1316,7 @@ nsBlockFrame::ReflowAppendedChildren(nsIPresContext* aCX,
   for (;;) {
     // Get the next content object
     nsIContentPtr kid = mContent->ChildAt(kidIndex);
-    if (nsnull == kid) {
+    if (kid.IsNull()) {
       result = frComplete;
       break;
     }
@@ -1340,7 +1338,6 @@ nsBlockFrame::ReflowAppendedChildren(nsIPresContext* aCX,
     } else if (nsnull == kidPrevInFlow) {
       // Create initial frame for the child
       nsIContentDelegate* kidDel;
-      nsresult fr;
       switch (kidDisplay->mDisplay) {
       case NS_STYLE_DISPLAY_BLOCK:
       case NS_STYLE_DISPLAY_LIST_ITEM:
@@ -1369,7 +1366,7 @@ nsBlockFrame::ReflowAppendedChildren(nsIPresContext* aCX,
 
       default:
         NS_ASSERTION(nsnull == kidPrevInFlow, "bad prev in flow");
-        fr = nsFrame::NewFrame(&kidFrame, kid, kidIndex, this);
+        nsFrame::NewFrame(&kidFrame, kid, kidIndex, this);
         break;
       }
       kidFrame->SetStyleContext(kidSC);
diff --git a/mozilla/layout/html/base/src/nsBlockFrame.cpp b/mozilla/layout/html/base/src/nsBlockFrame.cpp
index 84fd53b081b..841c30aa686 100644
--- a/mozilla/layout/html/base/src/nsBlockFrame.cpp
+++ b/mozilla/layout/html/base/src/nsBlockFrame.cpp
@@ -1162,7 +1162,6 @@ nsBlockFrame::ReflowMappedChildren(nsIPresContext* aCX,
 
   PRBool result = PR_TRUE;
   nsIFrame* kidFrame;
-  nsIFrame* prevKidFrame = nsnull;
 
   for (kidFrame = mFirstChild; nsnull != kidFrame; ) {
     nsIContentPtr kid;
@@ -1218,7 +1217,6 @@ nsBlockFrame::ReflowMappedChildren(nsIPresContext* aCX,
     }
 
     // Get the next child frame
-    prevKidFrame = kidFrame;
     kidFrame->GetNextSibling(kidFrame);
   }
 
@@ -1255,7 +1253,7 @@ PRBool nsBlockFrame::MoreToReflow(nsIPresContext* aCX)
     // Get the next content object that we would like to reflow
     PRInt32 kidIndex = NextChildOffset();
     nsIContentPtr kid = mContent->ChildAt(kidIndex);
-    if (nsnull != kid) {
+    if (kid.IsNotNull()) {
       // Resolve style for the kid
       nsIStyleContextPtr kidSC = aCX->ResolveStyleContextFor(kid, this);
       nsStyleDisplay* kidStyleDisplay = (nsStyleDisplay*)
@@ -1318,7 +1316,7 @@ nsBlockFrame::ReflowAppendedChildren(nsIPresContext* aCX,
   for (;;) {
     // Get the next content object
     nsIContentPtr kid = mContent->ChildAt(kidIndex);
-    if (nsnull == kid) {
+    if (kid.IsNull()) {
       result = frComplete;
       break;
     }
@@ -1340,7 +1338,6 @@ nsBlockFrame::ReflowAppendedChildren(nsIPresContext* aCX,
     } else if (nsnull == kidPrevInFlow) {
       // Create initial frame for the child
       nsIContentDelegate* kidDel;
-      nsresult fr;
       switch (kidDisplay->mDisplay) {
       case NS_STYLE_DISPLAY_BLOCK:
       case NS_STYLE_DISPLAY_LIST_ITEM:
@@ -1369,7 +1366,7 @@ nsBlockFrame::ReflowAppendedChildren(nsIPresContext* aCX,
 
       default:
         NS_ASSERTION(nsnull == kidPrevInFlow, "bad prev in flow");
-        fr = nsFrame::NewFrame(&kidFrame, kid, kidIndex, this);
+        nsFrame::NewFrame(&kidFrame, kid, kidIndex, this);
         break;
       }
       kidFrame->SetStyleContext(kidSC);
diff --git a/mozilla/layout/html/base/src/nsBlockReflowState.cpp b/mozilla/layout/html/base/src/nsBlockReflowState.cpp
index 84fd53b081b..841c30aa686 100644
--- a/mozilla/layout/html/base/src/nsBlockReflowState.cpp
+++ b/mozilla/layout/html/base/src/nsBlockReflowState.cpp
@@ -1162,7 +1162,6 @@ nsBlockFrame::ReflowMappedChildren(nsIPresContext* aCX,
 
   PRBool result = PR_TRUE;
   nsIFrame* kidFrame;
-  nsIFrame* prevKidFrame = nsnull;
 
   for (kidFrame = mFirstChild; nsnull != kidFrame; ) {
     nsIContentPtr kid;
@@ -1218,7 +1217,6 @@ nsBlockFrame::ReflowMappedChildren(nsIPresContext* aCX,
     }
 
     // Get the next child frame
-    prevKidFrame = kidFrame;
     kidFrame->GetNextSibling(kidFrame);
   }
 
@@ -1255,7 +1253,7 @@ PRBool nsBlockFrame::MoreToReflow(nsIPresContext* aCX)
     // Get the next content object that we would like to reflow
     PRInt32 kidIndex = NextChildOffset();
     nsIContentPtr kid = mContent->ChildAt(kidIndex);
-    if (nsnull != kid) {
+    if (kid.IsNotNull()) {
       // Resolve style for the kid
       nsIStyleContextPtr kidSC = aCX->ResolveStyleContextFor(kid, this);
       nsStyleDisplay* kidStyleDisplay = (nsStyleDisplay*)
@@ -1318,7 +1316,7 @@ nsBlockFrame::ReflowAppendedChildren(nsIPresContext* aCX,
   for (;;) {
     // Get the next content object
     nsIContentPtr kid = mContent->ChildAt(kidIndex);
-    if (nsnull == kid) {
+    if (kid.IsNull()) {
       result = frComplete;
       break;
     }
@@ -1340,7 +1338,6 @@ nsBlockFrame::ReflowAppendedChildren(nsIPresContext* aCX,
     } else if (nsnull == kidPrevInFlow) {
       // Create initial frame for the child
       nsIContentDelegate* kidDel;
-      nsresult fr;
       switch (kidDisplay->mDisplay) {
       case NS_STYLE_DISPLAY_BLOCK:
       case NS_STYLE_DISPLAY_LIST_ITEM:
@@ -1369,7 +1366,7 @@ nsBlockFrame::ReflowAppendedChildren(nsIPresContext* aCX,
 
       default:
         NS_ASSERTION(nsnull == kidPrevInFlow, "bad prev in flow");
-        fr = nsFrame::NewFrame(&kidFrame, kid, kidIndex, this);
+        nsFrame::NewFrame(&kidFrame, kid, kidIndex, this);
         break;
       }
       kidFrame->SetStyleContext(kidSC);
diff --git a/mozilla/layout/html/base/src/nsBlockReflowState.h b/mozilla/layout/html/base/src/nsBlockReflowState.h
index 84fd53b081b..841c30aa686 100644
--- a/mozilla/layout/html/base/src/nsBlockReflowState.h
+++ b/mozilla/layout/html/base/src/nsBlockReflowState.h
@@ -1162,7 +1162,6 @@ nsBlockFrame::ReflowMappedChildren(nsIPresContext* aCX,
 
   PRBool result = PR_TRUE;
   nsIFrame* kidFrame;
-  nsIFrame* prevKidFrame = nsnull;
 
   for (kidFrame = mFirstChild; nsnull != kidFrame; ) {
     nsIContentPtr kid;
@@ -1218,7 +1217,6 @@ nsBlockFrame::ReflowMappedChildren(nsIPresContext* aCX,
     }
 
     // Get the next child frame
-    prevKidFrame = kidFrame;
     kidFrame->GetNextSibling(kidFrame);
   }
 
@@ -1255,7 +1253,7 @@ PRBool nsBlockFrame::MoreToReflow(nsIPresContext* aCX)
     // Get the next content object that we would like to reflow
     PRInt32 kidIndex = NextChildOffset();
     nsIContentPtr kid = mContent->ChildAt(kidIndex);
-    if (nsnull != kid) {
+    if (kid.IsNotNull()) {
       // Resolve style for the kid
       nsIStyleContextPtr kidSC = aCX->ResolveStyleContextFor(kid, this);
       nsStyleDisplay* kidStyleDisplay = (nsStyleDisplay*)
@@ -1318,7 +1316,7 @@ nsBlockFrame::ReflowAppendedChildren(nsIPresContext* aCX,
   for (;;) {
     // Get the next content object
     nsIContentPtr kid = mContent->ChildAt(kidIndex);
-    if (nsnull == kid) {
+    if (kid.IsNull()) {
       result = frComplete;
       break;
     }
@@ -1340,7 +1338,6 @@ nsBlockFrame::ReflowAppendedChildren(nsIPresContext* aCX,
     } else if (nsnull == kidPrevInFlow) {
       // Create initial frame for the child
       nsIContentDelegate* kidDel;
-      nsresult fr;
       switch (kidDisplay->mDisplay) {
       case NS_STYLE_DISPLAY_BLOCK:
       case NS_STYLE_DISPLAY_LIST_ITEM:
@@ -1369,7 +1366,7 @@ nsBlockFrame::ReflowAppendedChildren(nsIPresContext* aCX,
 
       default:
         NS_ASSERTION(nsnull == kidPrevInFlow, "bad prev in flow");
-        fr = nsFrame::NewFrame(&kidFrame, kid, kidIndex, this);
+        nsFrame::NewFrame(&kidFrame, kid, kidIndex, this);
         break;
       }
       kidFrame->SetStyleContext(kidSC);
diff --git a/mozilla/layout/html/base/src/nsBodyFrame.cpp b/mozilla/layout/html/base/src/nsBodyFrame.cpp
index 4dea2553c1f..35ae0d1e45c 100644
--- a/mozilla/layout/html/base/src/nsBodyFrame.cpp
+++ b/mozilla/layout/html/base/src/nsBodyFrame.cpp
@@ -220,7 +220,6 @@ NS_METHOD nsBodyFrame::VerifyTree() const
   NS_ASSERTION(mFirstContentOffset <= mLastContentOffset, "bad offsets");
 
   // Verify child content offsets
-  PRInt32 offset = mFirstContentOffset;
   nsIFrame* child = mFirstChild;
   while (nsnull != child) {
     // Make sure that the child's tree is valid
diff --git a/mozilla/layout/html/base/src/nsColumnFrame.cpp b/mozilla/layout/html/base/src/nsColumnFrame.cpp
index c3ed081ea43..72f70cd81a3 100644
--- a/mozilla/layout/html/base/src/nsColumnFrame.cpp
+++ b/mozilla/layout/html/base/src/nsColumnFrame.cpp
@@ -648,8 +648,6 @@ ColumnFrame::ReflowUnmappedChildren(nsIPresContext*    aPresContext,
     }
   }
 
-  PRBool originalLastContentIsComplete = mLastContentIsComplete;
-
   // Place our children, one at a time, until we are out of children
   nsSize    kidMaxElementSize;
   nsSize*   pKidMaxElementSize = (nsnull != aMaxElementSize) ? &kidMaxElementSize : nsnull;
@@ -661,7 +659,7 @@ ColumnFrame::ReflowUnmappedChildren(nsIPresContext*    aPresContext,
   for (;;) {
     // Get the next content object
     nsIContentPtr kid = mContent->ChildAt(kidIndex);
-    if (nsnull == kid) {
+    if (kid.IsNull()) {
       result = frComplete;
       break;
     }
diff --git a/mozilla/layout/html/base/src/nsDOMIterator.cpp b/mozilla/layout/html/base/src/nsDOMIterator.cpp
index e1859075358..5edfdb89d57 100644
--- a/mozilla/layout/html/base/src/nsDOMIterator.cpp
+++ b/mozilla/layout/html/base/src/nsDOMIterator.cpp
@@ -19,7 +19,6 @@
 #include "nsDOMIterator.h"
 #include "nsIDOMNode.h"
 
-static NS_DEFINE_IID(kIContentIID, NS_ICONTENT_IID);
 static NS_DEFINE_IID(kIDOMNodeIID, NS_IDOMNODE_IID);
 
 nsDOMIterator::nsDOMIterator(nsIContent &aContent) : mContent(aContent)
diff --git a/mozilla/layout/html/base/src/nsHRPart.cpp b/mozilla/layout/html/base/src/nsHRPart.cpp
index dac2cb82754..29ee02c424e 100644
--- a/mozilla/layout/html/base/src/nsHRPart.cpp
+++ b/mozilla/layout/html/base/src/nsHRPart.cpp
@@ -182,7 +182,6 @@ NS_METHOD HRuleFrame::Paint(nsIPresContext& aPresContext,
     // When a rule is not shaded, then we use a uniform color and
     // draw half-circles on the end points.
     aRenderingContext.SetColor (colors[0]);
-    float t2p = 1.0f / p2t;
     nscoord diameter = height;
     if ((diameter > width) || (diameter < nscoord(p2t * 3))) {
       // The half-circles on the ends of the rule aren't going to
diff --git a/mozilla/layout/html/base/src/nsTextContent.cpp b/mozilla/layout/html/base/src/nsTextContent.cpp
index a0caa0f43f7..35c2b4f1e94 100644
--- a/mozilla/layout/html/base/src/nsTextContent.cpp
+++ b/mozilla/layout/html/base/src/nsTextContent.cpp
@@ -991,7 +991,6 @@ NS_METHOD TextFrame::JustifyReflow(nsIPresContext* aCX, nscoord aAvailableSpace)
   // space and compress down whitespace.
   Text* txt = (Text*) mContent;
   const PRUnichar* cp = txt->mText + mContentOffset;
-  const PRUnichar* cpStart = cp;
   const PRUnichar* end = cp + mContentLength;
   PRUint32* wp = wp0;
   PRUint32* wpend = wp0 + maxWords;
diff --git a/mozilla/layout/html/forms/src/nsForm.cpp b/mozilla/layout/html/forms/src/nsForm.cpp
index 583a7489e17..d894c5980a8 100644
--- a/mozilla/layout/html/forms/src/nsForm.cpp
+++ b/mozilla/layout/html/forms/src/nsForm.cpp
@@ -98,7 +98,7 @@ public:
     return rv;
   }
 
-  NS_DECL_ISUPPORTS;
+  NS_DECL_ISUPPORTS
 
   virtual void OnRadioChecked(nsIFormControl& aRadio);
     
diff --git a/mozilla/layout/html/forms/src/nsInput.cpp b/mozilla/layout/html/forms/src/nsInput.cpp
index a5e7661d1d7..71a6e5a22ed 100644
--- a/mozilla/layout/html/forms/src/nsInput.cpp
+++ b/mozilla/layout/html/forms/src/nsInput.cpp
@@ -30,7 +30,7 @@
 #include "nsHTMLAtoms.h"
 #include "nsIView.h"
 #include "nsIViewManager.h"
-#include "nscoord.h"
+#include "nsCoord.h"
 #include "nsDebug.h"
 #include "nsIWidget.h"
 #include "nsHTMLForms.h"
diff --git a/mozilla/layout/html/forms/src/nsInputButton.cpp b/mozilla/layout/html/forms/src/nsInputButton.cpp
index fd99b91a33b..6acefade632 100644
--- a/mozilla/layout/html/forms/src/nsInputButton.cpp
+++ b/mozilla/layout/html/forms/src/nsInputButton.cpp
@@ -85,9 +85,9 @@ public:
 
   virtual void MouseClicked(nsIPresContext* aPresContext);
 
-  virtual const nsIID GetCID();
+  virtual const nsIID& GetCID();
 
-  virtual const nsIID GetIID();
+  virtual const nsIID& GetIID();
 
   nsInputButtonType GetButtonType() const;
 
@@ -311,14 +311,14 @@ nsInputButtonFrame::PostCreateWidget(nsIPresContext* aPresContext, nsIView *aVie
   NS_RELEASE(button);
 }
 
-const nsIID
+const nsIID&
 nsInputButtonFrame::GetIID()
 {
   static NS_DEFINE_IID(kButtonIID, NS_IBUTTON_IID);
   return kButtonIID;
 }
   
-const nsIID
+const nsIID&
 nsInputButtonFrame::GetCID()
 {
   static NS_DEFINE_IID(kButtonCID, NS_BUTTON_CID);
diff --git a/mozilla/layout/html/forms/src/nsInputCheckbox.cpp b/mozilla/layout/html/forms/src/nsInputCheckbox.cpp
index 5a2b8b7224b..1f5e482f021 100644
--- a/mozilla/layout/html/forms/src/nsInputCheckbox.cpp
+++ b/mozilla/layout/html/forms/src/nsInputCheckbox.cpp
@@ -39,9 +39,9 @@ public:
 
   virtual void PostCreateWidget(nsIPresContext* aPresContext, nsIView *aView);
 
-  virtual const nsIID GetCID();
+  virtual const nsIID& GetCID();
 
-  virtual const nsIID GetIID();
+  virtual const nsIID& GetIID();
 
   virtual void MouseClicked(nsIPresContext* aPresContext);
 
@@ -67,14 +67,14 @@ nsInputCheckboxFrame::~nsInputCheckboxFrame()
 }
 
 
-const nsIID
+const nsIID&
 nsInputCheckboxFrame::GetIID()
 {
   static NS_DEFINE_IID(kCheckboxIID, NS_ICHECKBUTTON_IID);
   return kCheckboxIID;
 }
   
-const nsIID
+const nsIID&
 nsInputCheckboxFrame::GetCID()
 {
   static NS_DEFINE_IID(kCheckboxCID, NS_CHECKBUTTON_CID);
diff --git a/mozilla/layout/html/forms/src/nsInputFrame.cpp b/mozilla/layout/html/forms/src/nsInputFrame.cpp
index 0344883f899..0147b5bd6d5 100644
--- a/mozilla/layout/html/forms/src/nsInputFrame.cpp
+++ b/mozilla/layout/html/forms/src/nsInputFrame.cpp
@@ -206,7 +206,7 @@ nsInputFrame::ResizeReflow(nsIPresContext* aPresContext,
     GetParentWithView(parWithView);
 	  parWithView->GetView(parView);
 
-	  const nsIID id = GetCID();
+	  const nsIID& id = GetCID();
     nsInputWidgetData* initData = GetWidgetInitData(); // needs to be deleted
 	  // initialize the view as hidden since we don't know the (x,y) until Paint
     result = view->Init(viewMan, boundBox, parView, &id, initData, nsnull, 0, nsnull,
@@ -277,14 +277,14 @@ nsInputFrame::GetWidget(nsIView* aView, nsIWidget** aWidget)
   }
 }
 
-const nsIID
+const nsIID&
 nsInputFrame::GetIID()
 {
   static NS_DEFINE_IID(kButtonIID, NS_IBUTTON_IID);
   return kButtonIID;
 }
   
-const nsIID
+const nsIID&
 nsInputFrame::GetCID()
 {
   static NS_DEFINE_IID(kButtonCID, NS_BUTTON_CID);
diff --git a/mozilla/layout/html/forms/src/nsInputFrame.h b/mozilla/layout/html/forms/src/nsInputFrame.h
index d9b002f38ab..3d4125ed6ea 100644
--- a/mozilla/layout/html/forms/src/nsInputFrame.h
+++ b/mozilla/layout/html/forms/src/nsInputFrame.h
@@ -28,10 +28,10 @@ class nsIView;
 class nsIPresContext;
 
 struct nsInputWidgetData {
-  DWORD arg1;
-  DWORD arg2;
-  DWORD arg3;
-  DWORD arg4;
+  PRInt32 arg1;
+  PRInt32 arg2;
+  PRInt32 arg3;
+  PRInt32 arg4;
 };
 
 /**
@@ -124,13 +124,13 @@ public:
     * Get the class id of the widget associated with this frame
     * @return the class id
     */
-  virtual const nsIID GetCID(); 
+  virtual const nsIID& GetCID(); 
 
   /**
     * Get the interface id of widget associated with this frame
     * @return the interface id
     */
-  virtual const nsIID GetIID(); 
+  virtual const nsIID& GetIID(); 
 
   /**
     * Get the widget associated with this frame
diff --git a/mozilla/layout/html/forms/src/nsInputRadio.cpp b/mozilla/layout/html/forms/src/nsInputRadio.cpp
index 290c2023fd3..79ff71b50dc 100644
--- a/mozilla/layout/html/forms/src/nsInputRadio.cpp
+++ b/mozilla/layout/html/forms/src/nsInputRadio.cpp
@@ -41,9 +41,9 @@ public:
 
   virtual void PostCreateWidget(nsIPresContext* aPresContext, nsIView *aView);
 
-  virtual const nsIID GetCID();
+  virtual const nsIID& GetCID();
 
-  virtual const nsIID GetIID();
+  virtual const nsIID& GetIID();
 
   virtual void MouseClicked(nsIPresContext* aPresContext);
 
@@ -69,14 +69,14 @@ nsInputRadioFrame::~nsInputRadioFrame()
 }
 
 
-const nsIID
+const nsIID&
 nsInputRadioFrame::GetIID()
 {
   static NS_DEFINE_IID(kRadioIID, NS_IRADIOBUTTON_IID);
   return kRadioIID;
 }
   
-const nsIID
+const nsIID&
 nsInputRadioFrame::GetCID()
 {
   static NS_DEFINE_IID(kRadioCID, NS_RADIOBUTTON_CID);
diff --git a/mozilla/layout/html/forms/src/nsInputText.cpp b/mozilla/layout/html/forms/src/nsInputText.cpp
index 3b3ebbd6e8f..9950e455a80 100644
--- a/mozilla/layout/html/forms/src/nsInputText.cpp
+++ b/mozilla/layout/html/forms/src/nsInputText.cpp
@@ -44,9 +44,9 @@ public:
 
   virtual void PostCreateWidget(nsIPresContext* aPresContext, nsIView *aView);
 
-  virtual const nsIID GetCID();
+  virtual const nsIID& GetCID();
 
-  virtual const nsIID GetIID();
+  virtual const nsIID& GetIID();
 
 protected:
 
@@ -71,7 +71,7 @@ nsInputTextFrame::~nsInputTextFrame()
 {
 }
 
-const nsIID
+const nsIID&
 nsInputTextFrame::GetIID()
 {
   static NS_DEFINE_IID(kTextIID, NS_ITEXTWIDGET_IID);
@@ -85,7 +85,7 @@ nsInputTextFrame::GetIID()
   }
 }
   
-const nsIID
+const nsIID&
 nsInputTextFrame::GetCID()
 {
   static NS_DEFINE_IID(kTextCID, NS_TEXTFIELD_CID);
diff --git a/mozilla/layout/html/forms/src/nsSelect.cpp b/mozilla/layout/html/forms/src/nsSelect.cpp
index 906fbd9426d..8f7b2a063d6 100644
--- a/mozilla/layout/html/forms/src/nsSelect.cpp
+++ b/mozilla/layout/html/forms/src/nsSelect.cpp
@@ -53,9 +53,9 @@ public:
 
   virtual void PostCreateWidget(nsIPresContext* aPresContext, nsIView *aView);
 
-  virtual const nsIID GetCID();
+  virtual const nsIID& GetCID();
 
-  virtual const nsIID GetIID();
+  virtual const nsIID& GetIID();
 
   PRBool IsComboBox();
 
@@ -153,7 +153,7 @@ nsSelectFrame::IsComboBox()
   return content->IsComboBox();
 }
 
-const nsIID
+const nsIID&
 nsSelectFrame::GetIID()
 {
   if (IsComboBox()) {
@@ -164,7 +164,7 @@ nsSelectFrame::GetIID()
   }
 }
   
-const nsIID
+const nsIID&
 nsSelectFrame::GetCID()
 {
   static NS_DEFINE_IID(kComboCID, NS_COMBOBOX_CID);
diff --git a/mozilla/layout/html/style/src/nsCSSStyleSheet.cpp b/mozilla/layout/html/style/src/nsCSSStyleSheet.cpp
index 472bf6e7372..b0fce35d38c 100644
--- a/mozilla/layout/html/style/src/nsCSSStyleSheet.cpp
+++ b/mozilla/layout/html/style/src/nsCSSStyleSheet.cpp
@@ -220,7 +220,7 @@ PRInt32 CSSStyleSheetImpl::RulesMatching(nsIPresContext* aPresContext,
     child = ((CSSStyleSheetImpl*)child)->mNext;
   }
 
-  PRInt32 count = ((nsnull != mRules) ? mRules->Count() : 0);
+  PRInt32 count = (mRules.IsNotNull() ? mRules->Count() : 0);
 
   for (PRInt32 index = 0; index < count; index++) {
     nsICSSStyleRulePtr rule = (nsICSSStyleRule*)mRules->ElementAt(index);
@@ -272,12 +272,12 @@ void CSSStyleSheetImpl::AppendStyleSheet(nsICSSStyleSheet* aSheet)
 {
   NS_PRECONDITION(nsnull != aSheet, "null arg");
 
-  if (nsnull == mFirstChild) {
+  if (mFirstChild.IsNull()) {
     mFirstChild.SetAddRef(aSheet);
   }
   else {
     nsICSSStyleSheet* child = mFirstChild;
-    while (nsnull != ((CSSStyleSheetImpl*)child)->mNext) {
+    while (((CSSStyleSheetImpl*)child)->mNext.IsNotNull()) {
       child = ((CSSStyleSheetImpl*)child)->mNext;
     }
     ((CSSStyleSheetImpl*)child)->mNext.SetAddRef(aSheet);
@@ -289,7 +289,7 @@ void CSSStyleSheetImpl::PrependStyleRule(nsICSSStyleRule* aRule)
   NS_PRECONDITION(nsnull != aRule, "null arg");
   //XXX replace this with a binary search?
   PRInt32 weight = aRule->GetWeight();
-  if (nsnull == mRules) {
+  if (mRules.IsNull()) {
     if (NS_OK != NS_NewISupportsArray(mRules.AssignPtr()))
       return;
   }
@@ -309,7 +309,7 @@ void CSSStyleSheetImpl::AppendStyleRule(nsICSSStyleRule* aRule)
 
   //XXX replace this with a binary search?
   PRInt32 weight = aRule->GetWeight();
-  if (nsnull == mRules) {
+  if (mRules.IsNull()) {
     if (NS_OK != NS_NewISupportsArray(mRules.AssignPtr()))
       return;
   }
@@ -343,7 +343,7 @@ void CSSStyleSheetImpl::List(FILE* out, PRInt32 aIndent) const
     child = ((CSSStyleSheetImpl*)child)->mNext;
   }
 
-  PRInt32 count = ((nsnull != mRules) ? mRules->Count() : 0);
+  PRInt32 count = (mRules.IsNotNull() ? mRules->Count() : 0);
 
   for (index = 0; index < count; index++) {
     nsICSSStyleRulePtr rule = (nsICSSStyleRule*)mRules->ElementAt(index);
diff --git a/mozilla/layout/html/table/src/nsCellLayoutData.cpp b/mozilla/layout/html/table/src/nsCellLayoutData.cpp
index 0bdc2434b9d..2e22a2327da 100644
--- a/mozilla/layout/html/table/src/nsCellLayoutData.cpp
+++ b/mozilla/layout/html/table/src/nsCellLayoutData.cpp
@@ -338,7 +338,7 @@ nsIStyleContext* nsCellLayoutData::FindHighestPrecedentBorder(nsVoidArray* aList
         style.SetAddRef(CompareCellBorders(style,aEdge, style2,aEdge));
       }
     }
-    if ((style != NULL) && (GetMargin(style,aEdge) != 0))
+    if (style.IsNotNull() && (GetMargin(style,aEdge) != 0))
       result = style.AddRef();
   }
   return result;
@@ -358,7 +358,7 @@ nsStyleSpacing* nsCellLayoutData::FindInnerBorder( nsIStyleContext* aStyle,
   {
     nsIStyleContextPtr style;
     nsIStyleContextPtr altStyle = FindHighestPrecedentBorder(aList,opposite);
-    if (altStyle != nsnull)
+    if (altStyle.IsNotNull())
       style.SetAddRef(CompareCellBorders(aStyle,aEdge,altStyle,opposite));
     else
       style.SetAddRef(aStyle);
@@ -421,7 +421,7 @@ nsStyleSpacing* nsCellLayoutData::FindOuterBorder( nsTableFrame* aTableFrame,
       // if the padding for the parent style is zero just
       // recursively call this routine
       PRInt32 padding = GetPadding(parentStyle,aEdge);
-      if ((parentStyle != NULL) && (padding == 0))
+      if (parentStyle.IsNotNull() && (padding == 0))
       {
         style = parentStyle;
         frame = parentFrame;
diff --git a/mozilla/layout/html/table/src/nsTableFrame.cpp b/mozilla/layout/html/table/src/nsTableFrame.cpp
index 9fc8d6a88ba..6a8b02b8b45 100644
--- a/mozilla/layout/html/table/src/nsTableFrame.cpp
+++ b/mozilla/layout/html/table/src/nsTableFrame.cpp
@@ -304,7 +304,7 @@ void nsTableFrame::ResetColumnLayoutData()
 
         // Check to see if cell the represents a top edge cell
         if (col == 0)
-          left == nsnull;
+          left = nsnull;
         else
         {
           cellData = cellMap->GetCellAt(row,col-1);
@@ -603,7 +603,7 @@ nsIFrame::ReflowStatus nsTableFrame::ResizeReflowPass1(nsIPresContext* aPresCont
    */
   for (;;) {
     nsIContentPtr kid = c->ChildAt(kidIndex);   // kid: REFCNT++
-    if (nsnull == kid) {
+    if (kid.IsNull()) {
       result = frComplete;
       break;
     }
@@ -616,7 +616,7 @@ nsIFrame::ReflowStatus nsTableFrame::ResizeReflowPass1(nsIPresContext* aPresCont
       // Resolve style
       nsIStyleContextPtr kidStyleContext =
         aPresContext->ResolveStyleContextFor(kid, this);
-      NS_ASSERTION(nsnull != kidStyleContext, "null style context for kid");
+      NS_ASSERTION(kidStyleContext.IsNotNull(), "null style context for kid");
 
       // SEC: TODO:  when content is appended or deleted, be sure to clear out the frame hierarchy!!!!
 
@@ -1385,7 +1385,7 @@ nsTableFrame::ReflowUnmappedChildren(nsIPresContext*      aPresContext,
   for (;;) {
     // Get the next content object
     nsIContentPtr kid = mContent->ChildAt(kidIndex);
-    if (nsnull == kid) {
+    if (kid.IsNull()) {
       result = frComplete;
       break;
     }
@@ -1629,7 +1629,7 @@ PRBool nsTableFrame::AssignFixedColumnWidths(nsIPresContext* aPresContext,
     nsColLayoutData * colData = (nsColLayoutData *)(columnLayoutData->ElementAt(colIndex));
     NS_ASSERTION(nsnull != colData, "bad column data");
     nsTableColPtr col = colData->GetCol();    // col: ADDREF++
-    NS_ASSERTION(nsnull != col, "bad col");
+    NS_ASSERTION(col.IsNotNull(), "bad col");
 
     // need to track min/max column width for setting min/max table widths
     PRInt32 minColWidth = 0;
@@ -2223,7 +2223,7 @@ void nsTableFrame::ShrinkWrapChildren(nsIPresContext* aPresContext,
     nsTableContentPtr kid;
      
     kidFrame->GetContent((nsIContent*&)(kid.AssignRef()));  // kid: REFCNT++
-    NS_ASSERTION(nsnull != kid, "bad kid");
+    NS_ASSERTION(kid.IsNotNull(), "bad kid");
     if (kid->GetType() == nsITableContent::kTableRowGroupType)
     {
       /* Step 1:  set the row height to the height of the tallest cell,
@@ -2507,7 +2507,7 @@ PRBool nsTableFrame::SetCellLayoutData(nsCellLayoutData * aData, nsTableCell *aC
         for (PRInt32 i=0; i<tableKidCount; i++)
         {
           nsTableContentPtr tableKid = (nsTableContent *)tablePart->ChildAt(i);
-          NS_ASSERTION(nsnull != tableKid, "bad kid");
+          NS_ASSERTION(tableKid.IsNotNull(), "bad kid");
           const int contentType = tableKid->GetType();
           if (contentType == nsITableContent::kTableColGroupType)
           {
@@ -2515,7 +2515,7 @@ PRBool nsTableFrame::SetCellLayoutData(nsCellLayoutData * aData, nsTableCell *aC
             for (PRInt32 j=0; j<colsInGroup; j++)
             {
               nsTableColPtr col = (nsTableCol *)tableKid->ChildAt(j);
-              NS_ASSERTION(nsnull != col, "bad content");
+              NS_ASSERTION(col.IsNotNull(), "bad content");
               nsColLayoutData *colData = new nsColLayoutData(col);
               mColumnLayoutData->AppendElement((void *)colData);
             }
diff --git a/mozilla/layout/html/table/src/nsTableOuterFrame.cpp b/mozilla/layout/html/table/src/nsTableOuterFrame.cpp
index 60acd628377..ed0e4bd87c5 100644
--- a/mozilla/layout/html/table/src/nsTableOuterFrame.cpp
+++ b/mozilla/layout/html/table/src/nsTableOuterFrame.cpp
@@ -887,7 +887,7 @@ nsTableOuterFrame::ReflowChild( nsIFrame*        aKidFrame,
     nsIStyleContextPtr captionStyleContext;
 
     aKidFrame->GetStyleContext(aPresContext, captionStyleContext.AssignRef());
-    NS_ASSERTION(nsnull != captionStyleContext, "null style context for caption");
+    NS_ASSERTION(captionStyleContext.IsNotNull(), "null style context for caption");
     nsStyleText* captionStyle =
       (nsStyleText*)captionStyleContext->GetData(kStyleTextSID);
     NS_ASSERTION(nsnull != captionStyle, "null style molecule for caption");
@@ -942,7 +942,7 @@ void nsTableOuterFrame::CreateChildFrames(nsIPresContext*  aPresContext)
   // Resolve style
   nsIStyleContextPtr kidStyleContext =
     aPresContext->ResolveStyleContextFor(mContent, this);
-  NS_ASSERTION(nsnull!=kidStyleContext, "bad style context for kid.");
+  NS_ASSERTION(kidStyleContext.IsNotNull(), "bad style context for kid.");
   mInnerTableFrame->SetStyleContext(kidStyleContext);
   mChildCount++;
   // Link child frame into the list of children
@@ -956,7 +956,7 @@ void nsTableOuterFrame::CreateChildFrames(nsIPresContext*  aPresContext)
   nsIFrame *lastTopCaption = nsnull;
   for (PRInt32 kidIndex=0; /* nada */ ;kidIndex++) {
     nsIContentPtr caption = mContent->ChildAt(kidIndex);   // caption: REFCNT++
-    if (nsnull == caption) {
+    if (caption.IsNull()) {
       break;
     }
     const PRInt32 contentType = ((nsTableContent *)(nsIContent*)caption)->GetType();
@@ -969,7 +969,7 @@ void nsTableOuterFrame::CreateChildFrames(nsIPresContext*  aPresContext)
       // Resolve style
       nsIStyleContextPtr captionStyleContext =
         aPresContext->ResolveStyleContextFor(caption, this);
-      NS_ASSERTION(nsnull!=captionStyleContext, "bad style context for caption.");
+      NS_ASSERTION(captionStyleContext.IsNotNull(), "bad style context for caption.");
       nsStyleText* captionStyle = 
         (nsStyleText*)captionStyleContext->GetData(kStyleTextSID);
       captionFrame->SetStyleContext(captionStyleContext);
@@ -1055,7 +1055,7 @@ nsTableOuterFrame::ResizeReflowTopCaptionsPass2(nsIPresContext*  aPresContext,
       nsIStyleContextPtr captionStyleContext;
        
       captionFrame->GetStyleContext(aPresContext, captionStyleContext.AssignRef());
-      NS_ASSERTION(nsnull != captionStyleContext, "null style context for caption");
+      NS_ASSERTION(captionStyleContext.IsNotNull(), "null style context for caption");
       nsStyleText* captionStyle =
         (nsStyleText*)captionStyleContext->GetData(kStyleTextSID);
       NS_ASSERTION(nsnull != captionStyle, "null style molecule for caption");
diff --git a/mozilla/layout/html/table/src/nsTableRowGroupFrame.cpp b/mozilla/layout/html/table/src/nsTableRowGroupFrame.cpp
index 411a05ed2a4..efc5c86d4af 100644
--- a/mozilla/layout/html/table/src/nsTableRowGroupFrame.cpp
+++ b/mozilla/layout/html/table/src/nsTableRowGroupFrame.cpp
@@ -714,7 +714,7 @@ nsTableRowGroupFrame::ReflowUnmappedChildren(nsIPresContext*      aPresContext,
   for (;;) {
     // Get the next content object
     nsIContentPtr kid = mContent->ChildAt(kidIndex);
-    if (nsnull == kid) {
+    if (kid.IsNull()) {
       result = frComplete;
       break;
     }
diff --git a/mozilla/layout/style/nsCSSStyleSheet.cpp b/mozilla/layout/style/nsCSSStyleSheet.cpp
index 472bf6e7372..b0fce35d38c 100644
--- a/mozilla/layout/style/nsCSSStyleSheet.cpp
+++ b/mozilla/layout/style/nsCSSStyleSheet.cpp
@@ -220,7 +220,7 @@ PRInt32 CSSStyleSheetImpl::RulesMatching(nsIPresContext* aPresContext,
     child = ((CSSStyleSheetImpl*)child)->mNext;
   }
 
-  PRInt32 count = ((nsnull != mRules) ? mRules->Count() : 0);
+  PRInt32 count = (mRules.IsNotNull() ? mRules->Count() : 0);
 
   for (PRInt32 index = 0; index < count; index++) {
     nsICSSStyleRulePtr rule = (nsICSSStyleRule*)mRules->ElementAt(index);
@@ -272,12 +272,12 @@ void CSSStyleSheetImpl::AppendStyleSheet(nsICSSStyleSheet* aSheet)
 {
   NS_PRECONDITION(nsnull != aSheet, "null arg");
 
-  if (nsnull == mFirstChild) {
+  if (mFirstChild.IsNull()) {
     mFirstChild.SetAddRef(aSheet);
   }
   else {
     nsICSSStyleSheet* child = mFirstChild;
-    while (nsnull != ((CSSStyleSheetImpl*)child)->mNext) {
+    while (((CSSStyleSheetImpl*)child)->mNext.IsNotNull()) {
       child = ((CSSStyleSheetImpl*)child)->mNext;
     }
     ((CSSStyleSheetImpl*)child)->mNext.SetAddRef(aSheet);
@@ -289,7 +289,7 @@ void CSSStyleSheetImpl::PrependStyleRule(nsICSSStyleRule* aRule)
   NS_PRECONDITION(nsnull != aRule, "null arg");
   //XXX replace this with a binary search?
   PRInt32 weight = aRule->GetWeight();
-  if (nsnull == mRules) {
+  if (mRules.IsNull()) {
     if (NS_OK != NS_NewISupportsArray(mRules.AssignPtr()))
       return;
   }
@@ -309,7 +309,7 @@ void CSSStyleSheetImpl::AppendStyleRule(nsICSSStyleRule* aRule)
 
   //XXX replace this with a binary search?
   PRInt32 weight = aRule->GetWeight();
-  if (nsnull == mRules) {
+  if (mRules.IsNull()) {
     if (NS_OK != NS_NewISupportsArray(mRules.AssignPtr()))
       return;
   }
@@ -343,7 +343,7 @@ void CSSStyleSheetImpl::List(FILE* out, PRInt32 aIndent) const
     child = ((CSSStyleSheetImpl*)child)->mNext;
   }
 
-  PRInt32 count = ((nsnull != mRules) ? mRules->Count() : 0);
+  PRInt32 count = (mRules.IsNotNull() ? mRules->Count() : 0);
 
   for (index = 0; index < count; index++) {
     nsICSSStyleRulePtr rule = (nsICSSStyleRule*)mRules->ElementAt(index);
diff --git a/mozilla/layout/tables/nsTableFrame.cpp b/mozilla/layout/tables/nsTableFrame.cpp
index 9fc8d6a88ba..6a8b02b8b45 100644
--- a/mozilla/layout/tables/nsTableFrame.cpp
+++ b/mozilla/layout/tables/nsTableFrame.cpp
@@ -304,7 +304,7 @@ void nsTableFrame::ResetColumnLayoutData()
 
         // Check to see if cell the represents a top edge cell
         if (col == 0)
-          left == nsnull;
+          left = nsnull;
         else
         {
           cellData = cellMap->GetCellAt(row,col-1);
@@ -603,7 +603,7 @@ nsIFrame::ReflowStatus nsTableFrame::ResizeReflowPass1(nsIPresContext* aPresCont
    */
   for (;;) {
     nsIContentPtr kid = c->ChildAt(kidIndex);   // kid: REFCNT++
-    if (nsnull == kid) {
+    if (kid.IsNull()) {
       result = frComplete;
       break;
     }
@@ -616,7 +616,7 @@ nsIFrame::ReflowStatus nsTableFrame::ResizeReflowPass1(nsIPresContext* aPresCont
       // Resolve style
       nsIStyleContextPtr kidStyleContext =
         aPresContext->ResolveStyleContextFor(kid, this);
-      NS_ASSERTION(nsnull != kidStyleContext, "null style context for kid");
+      NS_ASSERTION(kidStyleContext.IsNotNull(), "null style context for kid");
 
       // SEC: TODO:  when content is appended or deleted, be sure to clear out the frame hierarchy!!!!
 
@@ -1385,7 +1385,7 @@ nsTableFrame::ReflowUnmappedChildren(nsIPresContext*      aPresContext,
   for (;;) {
     // Get the next content object
     nsIContentPtr kid = mContent->ChildAt(kidIndex);
-    if (nsnull == kid) {
+    if (kid.IsNull()) {
       result = frComplete;
       break;
     }
@@ -1629,7 +1629,7 @@ PRBool nsTableFrame::AssignFixedColumnWidths(nsIPresContext* aPresContext,
     nsColLayoutData * colData = (nsColLayoutData *)(columnLayoutData->ElementAt(colIndex));
     NS_ASSERTION(nsnull != colData, "bad column data");
     nsTableColPtr col = colData->GetCol();    // col: ADDREF++
-    NS_ASSERTION(nsnull != col, "bad col");
+    NS_ASSERTION(col.IsNotNull(), "bad col");
 
     // need to track min/max column width for setting min/max table widths
     PRInt32 minColWidth = 0;
@@ -2223,7 +2223,7 @@ void nsTableFrame::ShrinkWrapChildren(nsIPresContext* aPresContext,
     nsTableContentPtr kid;
      
     kidFrame->GetContent((nsIContent*&)(kid.AssignRef()));  // kid: REFCNT++
-    NS_ASSERTION(nsnull != kid, "bad kid");
+    NS_ASSERTION(kid.IsNotNull(), "bad kid");
     if (kid->GetType() == nsITableContent::kTableRowGroupType)
     {
       /* Step 1:  set the row height to the height of the tallest cell,
@@ -2507,7 +2507,7 @@ PRBool nsTableFrame::SetCellLayoutData(nsCellLayoutData * aData, nsTableCell *aC
         for (PRInt32 i=0; i<tableKidCount; i++)
         {
           nsTableContentPtr tableKid = (nsTableContent *)tablePart->ChildAt(i);
-          NS_ASSERTION(nsnull != tableKid, "bad kid");
+          NS_ASSERTION(tableKid.IsNotNull(), "bad kid");
           const int contentType = tableKid->GetType();
           if (contentType == nsITableContent::kTableColGroupType)
           {
@@ -2515,7 +2515,7 @@ PRBool nsTableFrame::SetCellLayoutData(nsCellLayoutData * aData, nsTableCell *aC
             for (PRInt32 j=0; j<colsInGroup; j++)
             {
               nsTableColPtr col = (nsTableCol *)tableKid->ChildAt(j);
-              NS_ASSERTION(nsnull != col, "bad content");
+              NS_ASSERTION(col.IsNotNull(), "bad content");
               nsColLayoutData *colData = new nsColLayoutData(col);
               mColumnLayoutData->AppendElement((void *)colData);
             }
diff --git a/mozilla/layout/tables/nsTableOuterFrame.cpp b/mozilla/layout/tables/nsTableOuterFrame.cpp
index 60acd628377..ed0e4bd87c5 100644
--- a/mozilla/layout/tables/nsTableOuterFrame.cpp
+++ b/mozilla/layout/tables/nsTableOuterFrame.cpp
@@ -887,7 +887,7 @@ nsTableOuterFrame::ReflowChild( nsIFrame*        aKidFrame,
     nsIStyleContextPtr captionStyleContext;
 
     aKidFrame->GetStyleContext(aPresContext, captionStyleContext.AssignRef());
-    NS_ASSERTION(nsnull != captionStyleContext, "null style context for caption");
+    NS_ASSERTION(captionStyleContext.IsNotNull(), "null style context for caption");
     nsStyleText* captionStyle =
       (nsStyleText*)captionStyleContext->GetData(kStyleTextSID);
     NS_ASSERTION(nsnull != captionStyle, "null style molecule for caption");
@@ -942,7 +942,7 @@ void nsTableOuterFrame::CreateChildFrames(nsIPresContext*  aPresContext)
   // Resolve style
   nsIStyleContextPtr kidStyleContext =
     aPresContext->ResolveStyleContextFor(mContent, this);
-  NS_ASSERTION(nsnull!=kidStyleContext, "bad style context for kid.");
+  NS_ASSERTION(kidStyleContext.IsNotNull(), "bad style context for kid.");
   mInnerTableFrame->SetStyleContext(kidStyleContext);
   mChildCount++;
   // Link child frame into the list of children
@@ -956,7 +956,7 @@ void nsTableOuterFrame::CreateChildFrames(nsIPresContext*  aPresContext)
   nsIFrame *lastTopCaption = nsnull;
   for (PRInt32 kidIndex=0; /* nada */ ;kidIndex++) {
     nsIContentPtr caption = mContent->ChildAt(kidIndex);   // caption: REFCNT++
-    if (nsnull == caption) {
+    if (caption.IsNull()) {
       break;
     }
     const PRInt32 contentType = ((nsTableContent *)(nsIContent*)caption)->GetType();
@@ -969,7 +969,7 @@ void nsTableOuterFrame::CreateChildFrames(nsIPresContext*  aPresContext)
       // Resolve style
       nsIStyleContextPtr captionStyleContext =
         aPresContext->ResolveStyleContextFor(caption, this);
-      NS_ASSERTION(nsnull!=captionStyleContext, "bad style context for caption.");
+      NS_ASSERTION(captionStyleContext.IsNotNull(), "bad style context for caption.");
       nsStyleText* captionStyle = 
         (nsStyleText*)captionStyleContext->GetData(kStyleTextSID);
       captionFrame->SetStyleContext(captionStyleContext);
@@ -1055,7 +1055,7 @@ nsTableOuterFrame::ResizeReflowTopCaptionsPass2(nsIPresContext*  aPresContext,
       nsIStyleContextPtr captionStyleContext;
        
       captionFrame->GetStyleContext(aPresContext, captionStyleContext.AssignRef());
-      NS_ASSERTION(nsnull != captionStyleContext, "null style context for caption");
+      NS_ASSERTION(captionStyleContext.IsNotNull(), "null style context for caption");
       nsStyleText* captionStyle =
         (nsStyleText*)captionStyleContext->GetData(kStyleTextSID);
       NS_ASSERTION(nsnull != captionStyle, "null style molecule for caption");
diff --git a/mozilla/layout/tables/nsTableRowGroupFrame.cpp b/mozilla/layout/tables/nsTableRowGroupFrame.cpp
index 411a05ed2a4..efc5c86d4af 100644
--- a/mozilla/layout/tables/nsTableRowGroupFrame.cpp
+++ b/mozilla/layout/tables/nsTableRowGroupFrame.cpp
@@ -714,7 +714,7 @@ nsTableRowGroupFrame::ReflowUnmappedChildren(nsIPresContext*      aPresContext,
   for (;;) {
     // Get the next content object
     nsIContentPtr kid = mContent->ChildAt(kidIndex);
-    if (nsnull == kid) {
+    if (kid.IsNull()) {
       result = frComplete;
       break;
     }