diff --git a/mozilla/content/html/content/src/nsGenericHTMLElement.cpp b/mozilla/content/html/content/src/nsGenericHTMLElement.cpp
index 4c3619bfcac..3f1726d4ed1 100644
--- a/mozilla/content/html/content/src/nsGenericHTMLElement.cpp
+++ b/mozilla/content/html/content/src/nsGenericHTMLElement.cpp
@@ -114,7 +114,10 @@ public:
   virtual void DropReference();
   virtual nsresult GetCSSDeclaration(nsICSSDeclaration **aDecl,
                                      PRBool aAllocate);
-  virtual nsresult ParseDeclaration(const nsString& aDecl);
+  virtual nsresult SetCSSDeclaration(nsICSSDeclaration *aDecl);
+  virtual nsresult ParseDeclaration(const nsString& aDecl,
+                                    PRBool aParseOnlyOneDecl,
+                                    PRBool aClearOldDecl);
   virtual nsresult GetParent(nsISupports **aParent);
 
 protected:
@@ -229,8 +232,34 @@ nsDOMCSSAttributeDeclaration::GetCSSDeclaration(nsICSSDeclaration **aDecl,
   return result;
 }
 
+nsresult
+nsDOMCSSAttributeDeclaration::SetCSSDeclaration(nsICSSDeclaration *aDecl)
+{
+  nsHTMLValue val;
+  nsIStyleRule* rule;
+  nsICSSStyleRule*  cssRule;
+  nsresult result = NS_OK;
+
+  if (nsnull != mContent) {
+    mContent->GetHTMLAttribute(nsHTMLAtoms::style, val);
+    if (eHTMLUnit_ISupports == val.GetUnit()) {
+      rule = (nsIStyleRule*) val.GetISupportsValue();
+      result = rule->QueryInterface(kICSSStyleRuleIID, (void**)&cssRule);
+      if (NS_OK == result) {
+        cssRule->SetDeclaration(aDecl);
+        NS_RELEASE(cssRule);
+      }      
+      NS_RELEASE(rule);
+    }
+  }
+
+  return result;
+}
+
 nsresult 
-nsDOMCSSAttributeDeclaration::ParseDeclaration(const nsString& aDecl)
+nsDOMCSSAttributeDeclaration::ParseDeclaration(const nsString& aDecl,
+                                               PRBool aParseOnlyOneDecl,
+                                               PRBool aClearOldDecl)
 {
   nsICSSDeclaration *decl;
   nsresult result = GetCSSDeclaration(&decl, PR_TRUE);
@@ -265,9 +294,34 @@ nsDOMCSSAttributeDeclaration::ParseDeclaration(const nsString& aDecl)
       if (doc) {
         doc->BeginUpdate();
       }
-      result = cssParser->ParseAndAppendDeclaration(aDecl, baseURI, decl, &hint);
+      nsCOMPtr<nsICSSDeclaration> declClone;
+      decl->Clone(*getter_AddRefs(declClone));
+
+      if (aClearOldDecl) {
+        // This should be done with decl->Clear() once such a method exists.
+        nsAutoString propName;
+        PRUint32 count, i;
+
+        decl->Count(&count);
+
+        for (i = 0; i < count; i++) {
+          decl->GetNthProperty(0, propName);
+
+          nsCSSProperty prop = nsCSSProps::LookupProperty(propName);
+          nsCSSValue val;
+
+          decl->RemoveProperty(prop, val);
+        }
+      }
+
+      result = cssParser->ParseAndAppendDeclaration(aDecl, baseURI, decl,
+                                                    aParseOnlyOneDecl, &hint);
+      if (result == NS_CSS_PARSER_DROP_DECLARATION) {
+        SetCSSDeclaration(declClone);
+        result = NS_OK;
+      }
       if (doc) {
-        if (NS_SUCCEEDED(result)) {
+        if (NS_SUCCEEDED(result) && result != NS_CSS_PARSER_DROP_DECLARATION) {
           doc->AttributeChanged(mContent, kNameSpaceID_None, nsHTMLAtoms::style, hint);
         }
         doc->EndUpdate();
diff --git a/mozilla/content/html/style/public/nsICSSParser.h b/mozilla/content/html/style/public/nsICSSParser.h
index 3b0241e18fc..349cb71529b 100644
--- a/mozilla/content/html/style/public/nsICSSParser.h
+++ b/mozilla/content/html/style/public/nsICSSParser.h
@@ -72,6 +72,7 @@ public:
   NS_IMETHOD ParseAndAppendDeclaration(const nsString&    aBuffer,
                                        nsIURI*            aBaseURL,
                                        nsICSSDeclaration* aDeclaration,
+                                       PRBool             aParseOnlyOneDecl,
                                        PRInt32*           aHint) = 0;
 
   // Charset management method:
@@ -92,6 +93,10 @@ public:
 #define NS_CSS_GETINFO_CSS2         ((PRUint32) 0x00000004L)
 #define NS_CSS_GETINFO_CSS_FROSTING ((PRUint32) 0x00000008L)
 
+// Success code that can be returned from ParseAndAppendDeclaration()
+#define NS_CSS_PARSER_DROP_DECLARATION \
+  NS_ERROR_GENERATE_SUCCESS(NS_ERROR_MODULE_LAYOUT,1)
+
 extern NS_HTML nsresult
   NS_NewCSSParser(nsICSSParser** aInstancePtrResult);
 
diff --git a/mozilla/content/html/style/src/nsCSSParser.cpp b/mozilla/content/html/style/src/nsCSSParser.cpp
index a95e6183363..04ce62c183a 100644
--- a/mozilla/content/html/style/src/nsCSSParser.cpp
+++ b/mozilla/content/html/style/src/nsCSSParser.cpp
@@ -55,9 +55,6 @@ static NS_DEFINE_IID(kICSSParserIID, NS_ICSS_PARSER_IID);
 static NS_DEFINE_IID(kICSSStyleSheetIID, NS_ICSS_STYLE_SHEET_IID);
 static NS_DEFINE_IID(kIStyleSheetIID, NS_ISTYLE_SHEET_IID);
 
-#define NS_CSS_PARSER_DROP_DECLARATION \
-  NS_ERROR_GENERATE_SUCCESS(NS_ERROR_MODULE_LAYOUT,1)
-
 
 MOZ_DECL_CTOR_COUNTER(SelectorList);
 
@@ -149,6 +146,7 @@ public:
   NS_IMETHOD ParseAndAppendDeclaration(const nsString&    aBuffer,
                                        nsIURI*            aBaseURL,
                                        nsICSSDeclaration* aDeclaration,
+                                       PRBool             aParseOnlyOneDecl,
                                        PRInt32*           aHint);
 
   NS_IMETHOD GetCharset(/*out*/nsString &aCharsetDest) const;
@@ -555,6 +553,7 @@ NS_IMETHODIMP
 CSSParserImpl::ParseAndAppendDeclaration(const nsString&    aBuffer,
                                          nsIURI*            aBaseURL,
                                          nsICSSDeclaration* aDeclaration,
+                                         PRBool             aParseOnlyOneDecl,
                                          PRInt32*           aHint)
 {
 //  NS_ASSERTION(nsnull != aBaseURL, "need base URL");
@@ -581,15 +580,26 @@ CSSParserImpl::ParseAndAppendDeclaration(const nsString&    aBuffer,
 
   PRInt32 hint = NS_STYLE_HINT_NONE;
 
-  if (! ParseDeclaration(errorCode, aDeclaration, PR_FALSE, hint)) {
-    hint = NS_STYLE_HINT_NONE;
-  }
   if (nsnull != aHint) {
     *aHint = hint;
   }
 
+  do {
+    if (ParseDeclaration(errorCode, aDeclaration, PR_FALSE, hint)) {
+      if (aHint && hint > *aHint) {
+        *aHint = hint;
+      }
+    } else {
+      if (errorCode != -1) { // -1 means EOF so we ignore that
+        rv = errorCode;
+      }
+
+      break;
+    }
+  } while (!aParseOnlyOneDecl);
+
   ReleaseScanner();
-  return NS_OK;
+  return rv;
 }
 
 //----------------------------------------------------------------------
diff --git a/mozilla/content/html/style/src/nsCSSStyleRule.cpp b/mozilla/content/html/style/src/nsCSSStyleRule.cpp
index 15d31bcd17e..e6f76eb14e0 100644
--- a/mozilla/content/html/style/src/nsCSSStyleRule.cpp
+++ b/mozilla/content/html/style/src/nsCSSStyleRule.cpp
@@ -793,7 +793,10 @@ public:
   virtual void DropReference(void);
   virtual nsresult GetCSSDeclaration(nsICSSDeclaration **aDecl,
                                      PRBool aAllocate);
-  virtual nsresult ParseDeclaration(const nsString& aDecl);
+  virtual nsresult SetCSSDeclaration(nsICSSDeclaration *aDecl);
+  virtual nsresult ParseDeclaration(const nsString& aDecl,
+                                    PRBool aParseOnlyOneDecl,
+                                    PRBool aClearOldDecl);
   virtual nsresult GetParent(nsISupports **aParent);
 
 protected:
@@ -865,8 +868,20 @@ DOMCSSDeclarationImpl::GetCSSDeclaration(nsICSSDeclaration **aDecl,
   return NS_OK;
 }
 
+nsresult
+DOMCSSDeclarationImpl::SetCSSDeclaration(nsICSSDeclaration *aDecl)
+{
+  if (nsnull != mRule) {
+    mRule->SetDeclaration(aDecl);
+  }
+
+  return NS_OK;
+}
+
 nsresult 
-DOMCSSDeclarationImpl::ParseDeclaration(const nsString& aDecl)
+DOMCSSDeclarationImpl::ParseDeclaration(const nsString& aDecl,
+                                        PRBool aParseOnlyOneDecl,
+                                        PRBool aClearOldDecl)
 {
   nsICSSDeclaration *decl;
   nsresult result = GetCSSDeclaration(&decl, PR_TRUE);
@@ -904,9 +919,35 @@ DOMCSSDeclarationImpl::ParseDeclaration(const nsString& aDecl)
     }
 
     if (NS_SUCCEEDED(result)) {
+      nsCOMPtr<nsICSSDeclaration> declClone;
+      decl->Clone(*getter_AddRefs(declClone));
+      NS_ENSURE_TRUE(declClone, NS_ERROR_OUT_OF_MEMORY);
+
+      if (aClearOldDecl) {
+        // This should be done with decl->Clear() once such a method exists.
+        nsAutoString propName;
+        PRUint32 count, i;
+
+        decl->Count(&count);
+
+        for (i = 0; i < count; i++) {
+          decl->GetNthProperty(0, propName);
+
+          nsCSSProperty prop = nsCSSProps::LookupProperty(propName);
+          nsCSSValue val;
+ 
+          decl->RemoveProperty(prop, val);
+        }
+      }
+
       PRInt32 hint;
-      result = cssParser->ParseAndAppendDeclaration(aDecl, baseURI, decl, &hint);
-      if (NS_SUCCEEDED(result)) {
+      result = cssParser->ParseAndAppendDeclaration(aDecl, baseURI, decl,
+                                                    aParseOnlyOneDecl, &hint);
+
+      if (result == NS_CSS_PARSER_DROP_DECLARATION) {
+        SetCSSDeclaration(declClone);
+        result = NS_OK;
+      } else if (NS_SUCCEEDED(result)) {
         if (cssSheet) {
           cssSheet->SetModified(PR_TRUE);
         }
diff --git a/mozilla/content/html/style/src/nsDOMCSSDeclaration.cpp b/mozilla/content/html/style/src/nsDOMCSSDeclaration.cpp
index 091a24a46ca..28131a08784 100644
--- a/mozilla/content/html/style/src/nsDOMCSSDeclaration.cpp
+++ b/mozilla/content/html/style/src/nsDOMCSSDeclaration.cpp
@@ -247,7 +247,7 @@ nsDOMCSSDeclaration::SetProperty(const nsString& aPropertyName,
   declString.Append(aValue);
   declString.Append(aPriority);
 
-  return ParseDeclaration(declString);
+  return ParseDeclaration(declString, PR_TRUE, PR_FALSE);
 }
 
 NS_IMETHODIMP 
diff --git a/mozilla/content/html/style/src/nsDOMCSSDeclaration.h b/mozilla/content/html/style/src/nsDOMCSSDeclaration.h
index 167242c1c39..7f51d0bbe0b 100644
--- a/mozilla/content/html/style/src/nsDOMCSSDeclaration.h
+++ b/mozilla/content/html/style/src/nsDOMCSSDeclaration.h
@@ -64,8 +64,12 @@ public:
   virtual void DropReference() = 0;
   virtual nsresult GetCSSDeclaration(nsICSSDeclaration **aDecl,
                                      PRBool aAllocate) = 0;
+  // Note! This will only set the declaration if a style rule already exists
+  virtual nsresult SetCSSDeclaration(nsICSSDeclaration *aDecl) = 0;
 
-  virtual nsresult ParseDeclaration(const nsString& aDecl) = 0;
+  virtual nsresult ParseDeclaration(const nsString& aDecl,
+                                    PRBool aParseOnlyOneDecl,
+                                    PRBool aClearOldDecl) = 0;
   virtual nsresult GetParent(nsISupports **aParent) = 0;
   
 protected:
diff --git a/mozilla/layout/html/content/src/nsGenericHTMLElement.cpp b/mozilla/layout/html/content/src/nsGenericHTMLElement.cpp
index 4c3619bfcac..3f1726d4ed1 100644
--- a/mozilla/layout/html/content/src/nsGenericHTMLElement.cpp
+++ b/mozilla/layout/html/content/src/nsGenericHTMLElement.cpp
@@ -114,7 +114,10 @@ public:
   virtual void DropReference();
   virtual nsresult GetCSSDeclaration(nsICSSDeclaration **aDecl,
                                      PRBool aAllocate);
-  virtual nsresult ParseDeclaration(const nsString& aDecl);
+  virtual nsresult SetCSSDeclaration(nsICSSDeclaration *aDecl);
+  virtual nsresult ParseDeclaration(const nsString& aDecl,
+                                    PRBool aParseOnlyOneDecl,
+                                    PRBool aClearOldDecl);
   virtual nsresult GetParent(nsISupports **aParent);
 
 protected:
@@ -229,8 +232,34 @@ nsDOMCSSAttributeDeclaration::GetCSSDeclaration(nsICSSDeclaration **aDecl,
   return result;
 }
 
+nsresult
+nsDOMCSSAttributeDeclaration::SetCSSDeclaration(nsICSSDeclaration *aDecl)
+{
+  nsHTMLValue val;
+  nsIStyleRule* rule;
+  nsICSSStyleRule*  cssRule;
+  nsresult result = NS_OK;
+
+  if (nsnull != mContent) {
+    mContent->GetHTMLAttribute(nsHTMLAtoms::style, val);
+    if (eHTMLUnit_ISupports == val.GetUnit()) {
+      rule = (nsIStyleRule*) val.GetISupportsValue();
+      result = rule->QueryInterface(kICSSStyleRuleIID, (void**)&cssRule);
+      if (NS_OK == result) {
+        cssRule->SetDeclaration(aDecl);
+        NS_RELEASE(cssRule);
+      }      
+      NS_RELEASE(rule);
+    }
+  }
+
+  return result;
+}
+
 nsresult 
-nsDOMCSSAttributeDeclaration::ParseDeclaration(const nsString& aDecl)
+nsDOMCSSAttributeDeclaration::ParseDeclaration(const nsString& aDecl,
+                                               PRBool aParseOnlyOneDecl,
+                                               PRBool aClearOldDecl)
 {
   nsICSSDeclaration *decl;
   nsresult result = GetCSSDeclaration(&decl, PR_TRUE);
@@ -265,9 +294,34 @@ nsDOMCSSAttributeDeclaration::ParseDeclaration(const nsString& aDecl)
       if (doc) {
         doc->BeginUpdate();
       }
-      result = cssParser->ParseAndAppendDeclaration(aDecl, baseURI, decl, &hint);
+      nsCOMPtr<nsICSSDeclaration> declClone;
+      decl->Clone(*getter_AddRefs(declClone));
+
+      if (aClearOldDecl) {
+        // This should be done with decl->Clear() once such a method exists.
+        nsAutoString propName;
+        PRUint32 count, i;
+
+        decl->Count(&count);
+
+        for (i = 0; i < count; i++) {
+          decl->GetNthProperty(0, propName);
+
+          nsCSSProperty prop = nsCSSProps::LookupProperty(propName);
+          nsCSSValue val;
+
+          decl->RemoveProperty(prop, val);
+        }
+      }
+
+      result = cssParser->ParseAndAppendDeclaration(aDecl, baseURI, decl,
+                                                    aParseOnlyOneDecl, &hint);
+      if (result == NS_CSS_PARSER_DROP_DECLARATION) {
+        SetCSSDeclaration(declClone);
+        result = NS_OK;
+      }
       if (doc) {
-        if (NS_SUCCEEDED(result)) {
+        if (NS_SUCCEEDED(result) && result != NS_CSS_PARSER_DROP_DECLARATION) {
           doc->AttributeChanged(mContent, kNameSpaceID_None, nsHTMLAtoms::style, hint);
         }
         doc->EndUpdate();
diff --git a/mozilla/layout/html/style/public/nsICSSParser.h b/mozilla/layout/html/style/public/nsICSSParser.h
index 3b0241e18fc..349cb71529b 100644
--- a/mozilla/layout/html/style/public/nsICSSParser.h
+++ b/mozilla/layout/html/style/public/nsICSSParser.h
@@ -72,6 +72,7 @@ public:
   NS_IMETHOD ParseAndAppendDeclaration(const nsString&    aBuffer,
                                        nsIURI*            aBaseURL,
                                        nsICSSDeclaration* aDeclaration,
+                                       PRBool             aParseOnlyOneDecl,
                                        PRInt32*           aHint) = 0;
 
   // Charset management method:
@@ -92,6 +93,10 @@ public:
 #define NS_CSS_GETINFO_CSS2         ((PRUint32) 0x00000004L)
 #define NS_CSS_GETINFO_CSS_FROSTING ((PRUint32) 0x00000008L)
 
+// Success code that can be returned from ParseAndAppendDeclaration()
+#define NS_CSS_PARSER_DROP_DECLARATION \
+  NS_ERROR_GENERATE_SUCCESS(NS_ERROR_MODULE_LAYOUT,1)
+
 extern NS_HTML nsresult
   NS_NewCSSParser(nsICSSParser** aInstancePtrResult);
 
diff --git a/mozilla/layout/html/style/src/nsCSSParser.cpp b/mozilla/layout/html/style/src/nsCSSParser.cpp
index a95e6183363..04ce62c183a 100644
--- a/mozilla/layout/html/style/src/nsCSSParser.cpp
+++ b/mozilla/layout/html/style/src/nsCSSParser.cpp
@@ -55,9 +55,6 @@ static NS_DEFINE_IID(kICSSParserIID, NS_ICSS_PARSER_IID);
 static NS_DEFINE_IID(kICSSStyleSheetIID, NS_ICSS_STYLE_SHEET_IID);
 static NS_DEFINE_IID(kIStyleSheetIID, NS_ISTYLE_SHEET_IID);
 
-#define NS_CSS_PARSER_DROP_DECLARATION \
-  NS_ERROR_GENERATE_SUCCESS(NS_ERROR_MODULE_LAYOUT,1)
-
 
 MOZ_DECL_CTOR_COUNTER(SelectorList);
 
@@ -149,6 +146,7 @@ public:
   NS_IMETHOD ParseAndAppendDeclaration(const nsString&    aBuffer,
                                        nsIURI*            aBaseURL,
                                        nsICSSDeclaration* aDeclaration,
+                                       PRBool             aParseOnlyOneDecl,
                                        PRInt32*           aHint);
 
   NS_IMETHOD GetCharset(/*out*/nsString &aCharsetDest) const;
@@ -555,6 +553,7 @@ NS_IMETHODIMP
 CSSParserImpl::ParseAndAppendDeclaration(const nsString&    aBuffer,
                                          nsIURI*            aBaseURL,
                                          nsICSSDeclaration* aDeclaration,
+                                         PRBool             aParseOnlyOneDecl,
                                          PRInt32*           aHint)
 {
 //  NS_ASSERTION(nsnull != aBaseURL, "need base URL");
@@ -581,15 +580,26 @@ CSSParserImpl::ParseAndAppendDeclaration(const nsString&    aBuffer,
 
   PRInt32 hint = NS_STYLE_HINT_NONE;
 
-  if (! ParseDeclaration(errorCode, aDeclaration, PR_FALSE, hint)) {
-    hint = NS_STYLE_HINT_NONE;
-  }
   if (nsnull != aHint) {
     *aHint = hint;
   }
 
+  do {
+    if (ParseDeclaration(errorCode, aDeclaration, PR_FALSE, hint)) {
+      if (aHint && hint > *aHint) {
+        *aHint = hint;
+      }
+    } else {
+      if (errorCode != -1) { // -1 means EOF so we ignore that
+        rv = errorCode;
+      }
+
+      break;
+    }
+  } while (!aParseOnlyOneDecl);
+
   ReleaseScanner();
-  return NS_OK;
+  return rv;
 }
 
 //----------------------------------------------------------------------
diff --git a/mozilla/layout/html/style/src/nsCSSStyleRule.cpp b/mozilla/layout/html/style/src/nsCSSStyleRule.cpp
index 15d31bcd17e..e6f76eb14e0 100644
--- a/mozilla/layout/html/style/src/nsCSSStyleRule.cpp
+++ b/mozilla/layout/html/style/src/nsCSSStyleRule.cpp
@@ -793,7 +793,10 @@ public:
   virtual void DropReference(void);
   virtual nsresult GetCSSDeclaration(nsICSSDeclaration **aDecl,
                                      PRBool aAllocate);
-  virtual nsresult ParseDeclaration(const nsString& aDecl);
+  virtual nsresult SetCSSDeclaration(nsICSSDeclaration *aDecl);
+  virtual nsresult ParseDeclaration(const nsString& aDecl,
+                                    PRBool aParseOnlyOneDecl,
+                                    PRBool aClearOldDecl);
   virtual nsresult GetParent(nsISupports **aParent);
 
 protected:
@@ -865,8 +868,20 @@ DOMCSSDeclarationImpl::GetCSSDeclaration(nsICSSDeclaration **aDecl,
   return NS_OK;
 }
 
+nsresult
+DOMCSSDeclarationImpl::SetCSSDeclaration(nsICSSDeclaration *aDecl)
+{
+  if (nsnull != mRule) {
+    mRule->SetDeclaration(aDecl);
+  }
+
+  return NS_OK;
+}
+
 nsresult 
-DOMCSSDeclarationImpl::ParseDeclaration(const nsString& aDecl)
+DOMCSSDeclarationImpl::ParseDeclaration(const nsString& aDecl,
+                                        PRBool aParseOnlyOneDecl,
+                                        PRBool aClearOldDecl)
 {
   nsICSSDeclaration *decl;
   nsresult result = GetCSSDeclaration(&decl, PR_TRUE);
@@ -904,9 +919,35 @@ DOMCSSDeclarationImpl::ParseDeclaration(const nsString& aDecl)
     }
 
     if (NS_SUCCEEDED(result)) {
+      nsCOMPtr<nsICSSDeclaration> declClone;
+      decl->Clone(*getter_AddRefs(declClone));
+      NS_ENSURE_TRUE(declClone, NS_ERROR_OUT_OF_MEMORY);
+
+      if (aClearOldDecl) {
+        // This should be done with decl->Clear() once such a method exists.
+        nsAutoString propName;
+        PRUint32 count, i;
+
+        decl->Count(&count);
+
+        for (i = 0; i < count; i++) {
+          decl->GetNthProperty(0, propName);
+
+          nsCSSProperty prop = nsCSSProps::LookupProperty(propName);
+          nsCSSValue val;
+ 
+          decl->RemoveProperty(prop, val);
+        }
+      }
+
       PRInt32 hint;
-      result = cssParser->ParseAndAppendDeclaration(aDecl, baseURI, decl, &hint);
-      if (NS_SUCCEEDED(result)) {
+      result = cssParser->ParseAndAppendDeclaration(aDecl, baseURI, decl,
+                                                    aParseOnlyOneDecl, &hint);
+
+      if (result == NS_CSS_PARSER_DROP_DECLARATION) {
+        SetCSSDeclaration(declClone);
+        result = NS_OK;
+      } else if (NS_SUCCEEDED(result)) {
         if (cssSheet) {
           cssSheet->SetModified(PR_TRUE);
         }
diff --git a/mozilla/layout/html/style/src/nsDOMCSSDeclaration.cpp b/mozilla/layout/html/style/src/nsDOMCSSDeclaration.cpp
index 091a24a46ca..28131a08784 100644
--- a/mozilla/layout/html/style/src/nsDOMCSSDeclaration.cpp
+++ b/mozilla/layout/html/style/src/nsDOMCSSDeclaration.cpp
@@ -247,7 +247,7 @@ nsDOMCSSDeclaration::SetProperty(const nsString& aPropertyName,
   declString.Append(aValue);
   declString.Append(aPriority);
 
-  return ParseDeclaration(declString);
+  return ParseDeclaration(declString, PR_TRUE, PR_FALSE);
 }
 
 NS_IMETHODIMP 
diff --git a/mozilla/layout/html/style/src/nsDOMCSSDeclaration.h b/mozilla/layout/html/style/src/nsDOMCSSDeclaration.h
index 167242c1c39..7f51d0bbe0b 100644
--- a/mozilla/layout/html/style/src/nsDOMCSSDeclaration.h
+++ b/mozilla/layout/html/style/src/nsDOMCSSDeclaration.h
@@ -64,8 +64,12 @@ public:
   virtual void DropReference() = 0;
   virtual nsresult GetCSSDeclaration(nsICSSDeclaration **aDecl,
                                      PRBool aAllocate) = 0;
+  // Note! This will only set the declaration if a style rule already exists
+  virtual nsresult SetCSSDeclaration(nsICSSDeclaration *aDecl) = 0;
 
-  virtual nsresult ParseDeclaration(const nsString& aDecl) = 0;
+  virtual nsresult ParseDeclaration(const nsString& aDecl,
+                                    PRBool aParseOnlyOneDecl,
+                                    PRBool aClearOldDecl) = 0;
   virtual nsresult GetParent(nsISupports **aParent) = 0;
   
 protected:
diff --git a/mozilla/layout/style/nsCSSParser.cpp b/mozilla/layout/style/nsCSSParser.cpp
index a95e6183363..04ce62c183a 100644
--- a/mozilla/layout/style/nsCSSParser.cpp
+++ b/mozilla/layout/style/nsCSSParser.cpp
@@ -55,9 +55,6 @@ static NS_DEFINE_IID(kICSSParserIID, NS_ICSS_PARSER_IID);
 static NS_DEFINE_IID(kICSSStyleSheetIID, NS_ICSS_STYLE_SHEET_IID);
 static NS_DEFINE_IID(kIStyleSheetIID, NS_ISTYLE_SHEET_IID);
 
-#define NS_CSS_PARSER_DROP_DECLARATION \
-  NS_ERROR_GENERATE_SUCCESS(NS_ERROR_MODULE_LAYOUT,1)
-
 
 MOZ_DECL_CTOR_COUNTER(SelectorList);
 
@@ -149,6 +146,7 @@ public:
   NS_IMETHOD ParseAndAppendDeclaration(const nsString&    aBuffer,
                                        nsIURI*            aBaseURL,
                                        nsICSSDeclaration* aDeclaration,
+                                       PRBool             aParseOnlyOneDecl,
                                        PRInt32*           aHint);
 
   NS_IMETHOD GetCharset(/*out*/nsString &aCharsetDest) const;
@@ -555,6 +553,7 @@ NS_IMETHODIMP
 CSSParserImpl::ParseAndAppendDeclaration(const nsString&    aBuffer,
                                          nsIURI*            aBaseURL,
                                          nsICSSDeclaration* aDeclaration,
+                                         PRBool             aParseOnlyOneDecl,
                                          PRInt32*           aHint)
 {
 //  NS_ASSERTION(nsnull != aBaseURL, "need base URL");
@@ -581,15 +580,26 @@ CSSParserImpl::ParseAndAppendDeclaration(const nsString&    aBuffer,
 
   PRInt32 hint = NS_STYLE_HINT_NONE;
 
-  if (! ParseDeclaration(errorCode, aDeclaration, PR_FALSE, hint)) {
-    hint = NS_STYLE_HINT_NONE;
-  }
   if (nsnull != aHint) {
     *aHint = hint;
   }
 
+  do {
+    if (ParseDeclaration(errorCode, aDeclaration, PR_FALSE, hint)) {
+      if (aHint && hint > *aHint) {
+        *aHint = hint;
+      }
+    } else {
+      if (errorCode != -1) { // -1 means EOF so we ignore that
+        rv = errorCode;
+      }
+
+      break;
+    }
+  } while (!aParseOnlyOneDecl);
+
   ReleaseScanner();
-  return NS_OK;
+  return rv;
 }
 
 //----------------------------------------------------------------------
diff --git a/mozilla/layout/style/nsCSSStyleRule.cpp b/mozilla/layout/style/nsCSSStyleRule.cpp
index 15d31bcd17e..e6f76eb14e0 100644
--- a/mozilla/layout/style/nsCSSStyleRule.cpp
+++ b/mozilla/layout/style/nsCSSStyleRule.cpp
@@ -793,7 +793,10 @@ public:
   virtual void DropReference(void);
   virtual nsresult GetCSSDeclaration(nsICSSDeclaration **aDecl,
                                      PRBool aAllocate);
-  virtual nsresult ParseDeclaration(const nsString& aDecl);
+  virtual nsresult SetCSSDeclaration(nsICSSDeclaration *aDecl);
+  virtual nsresult ParseDeclaration(const nsString& aDecl,
+                                    PRBool aParseOnlyOneDecl,
+                                    PRBool aClearOldDecl);
   virtual nsresult GetParent(nsISupports **aParent);
 
 protected:
@@ -865,8 +868,20 @@ DOMCSSDeclarationImpl::GetCSSDeclaration(nsICSSDeclaration **aDecl,
   return NS_OK;
 }
 
+nsresult
+DOMCSSDeclarationImpl::SetCSSDeclaration(nsICSSDeclaration *aDecl)
+{
+  if (nsnull != mRule) {
+    mRule->SetDeclaration(aDecl);
+  }
+
+  return NS_OK;
+}
+
 nsresult 
-DOMCSSDeclarationImpl::ParseDeclaration(const nsString& aDecl)
+DOMCSSDeclarationImpl::ParseDeclaration(const nsString& aDecl,
+                                        PRBool aParseOnlyOneDecl,
+                                        PRBool aClearOldDecl)
 {
   nsICSSDeclaration *decl;
   nsresult result = GetCSSDeclaration(&decl, PR_TRUE);
@@ -904,9 +919,35 @@ DOMCSSDeclarationImpl::ParseDeclaration(const nsString& aDecl)
     }
 
     if (NS_SUCCEEDED(result)) {
+      nsCOMPtr<nsICSSDeclaration> declClone;
+      decl->Clone(*getter_AddRefs(declClone));
+      NS_ENSURE_TRUE(declClone, NS_ERROR_OUT_OF_MEMORY);
+
+      if (aClearOldDecl) {
+        // This should be done with decl->Clear() once such a method exists.
+        nsAutoString propName;
+        PRUint32 count, i;
+
+        decl->Count(&count);
+
+        for (i = 0; i < count; i++) {
+          decl->GetNthProperty(0, propName);
+
+          nsCSSProperty prop = nsCSSProps::LookupProperty(propName);
+          nsCSSValue val;
+ 
+          decl->RemoveProperty(prop, val);
+        }
+      }
+
       PRInt32 hint;
-      result = cssParser->ParseAndAppendDeclaration(aDecl, baseURI, decl, &hint);
-      if (NS_SUCCEEDED(result)) {
+      result = cssParser->ParseAndAppendDeclaration(aDecl, baseURI, decl,
+                                                    aParseOnlyOneDecl, &hint);
+
+      if (result == NS_CSS_PARSER_DROP_DECLARATION) {
+        SetCSSDeclaration(declClone);
+        result = NS_OK;
+      } else if (NS_SUCCEEDED(result)) {
         if (cssSheet) {
           cssSheet->SetModified(PR_TRUE);
         }
diff --git a/mozilla/layout/style/nsDOMCSSDeclaration.cpp b/mozilla/layout/style/nsDOMCSSDeclaration.cpp
index 091a24a46ca..28131a08784 100644
--- a/mozilla/layout/style/nsDOMCSSDeclaration.cpp
+++ b/mozilla/layout/style/nsDOMCSSDeclaration.cpp
@@ -247,7 +247,7 @@ nsDOMCSSDeclaration::SetProperty(const nsString& aPropertyName,
   declString.Append(aValue);
   declString.Append(aPriority);
 
-  return ParseDeclaration(declString);
+  return ParseDeclaration(declString, PR_TRUE, PR_FALSE);
 }
 
 NS_IMETHODIMP 
diff --git a/mozilla/layout/style/nsDOMCSSDeclaration.h b/mozilla/layout/style/nsDOMCSSDeclaration.h
index 167242c1c39..7f51d0bbe0b 100644
--- a/mozilla/layout/style/nsDOMCSSDeclaration.h
+++ b/mozilla/layout/style/nsDOMCSSDeclaration.h
@@ -64,8 +64,12 @@ public:
   virtual void DropReference() = 0;
   virtual nsresult GetCSSDeclaration(nsICSSDeclaration **aDecl,
                                      PRBool aAllocate) = 0;
+  // Note! This will only set the declaration if a style rule already exists
+  virtual nsresult SetCSSDeclaration(nsICSSDeclaration *aDecl) = 0;
 
-  virtual nsresult ParseDeclaration(const nsString& aDecl) = 0;
+  virtual nsresult ParseDeclaration(const nsString& aDecl,
+                                    PRBool aParseOnlyOneDecl,
+                                    PRBool aClearOldDecl) = 0;
   virtual nsresult GetParent(nsISupports **aParent) = 0;
   
 protected:
diff --git a/mozilla/layout/style/nsICSSParser.h b/mozilla/layout/style/nsICSSParser.h
index 3b0241e18fc..349cb71529b 100644
--- a/mozilla/layout/style/nsICSSParser.h
+++ b/mozilla/layout/style/nsICSSParser.h
@@ -72,6 +72,7 @@ public:
   NS_IMETHOD ParseAndAppendDeclaration(const nsString&    aBuffer,
                                        nsIURI*            aBaseURL,
                                        nsICSSDeclaration* aDeclaration,
+                                       PRBool             aParseOnlyOneDecl,
                                        PRInt32*           aHint) = 0;
 
   // Charset management method:
@@ -92,6 +93,10 @@ public:
 #define NS_CSS_GETINFO_CSS2         ((PRUint32) 0x00000004L)
 #define NS_CSS_GETINFO_CSS_FROSTING ((PRUint32) 0x00000008L)
 
+// Success code that can be returned from ParseAndAppendDeclaration()
+#define NS_CSS_PARSER_DROP_DECLARATION \
+  NS_ERROR_GENERATE_SUCCESS(NS_ERROR_MODULE_LAYOUT,1)
+
 extern NS_HTML nsresult
   NS_NewCSSParser(nsICSSParser** aInstancePtrResult);