diff --git a/mozilla/content/base/src/nsDOMAttribute.cpp b/mozilla/content/base/src/nsDOMAttribute.cpp
index 05f315b7d8b..b93e22e2b4c 100644
--- a/mozilla/content/base/src/nsDOMAttribute.cpp
+++ b/mozilla/content/base/src/nsDOMAttribute.cpp
@@ -94,22 +94,37 @@ nsDOMAttribute::QueryInterface(REFNSIID aIID, void** aInstancePtr)
 NS_IMPL_ADDREF(nsDOMAttribute)
 NS_IMPL_RELEASE(nsDOMAttribute)
 
-void 
+NS_IMETHODIMP
 nsDOMAttribute::DropReference()
 {
   mContent = nsnull;
+
+  return NS_OK;
 }
 
-void 
+NS_IMETHODIMP
 nsDOMAttribute::SetContent(nsIContent* aContent)
 {
   mContent = aContent;
+
+  return NS_OK;
 }
 
-void 
+NS_IMETHODIMP
+nsDOMAttribute::GetContent(nsIContent** aContent)
+{
+  *aContent = mContent;
+  NS_IF_ADDREF(mContent);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
 nsDOMAttribute::SetName(const nsString& aName)
 {
   mName=aName;
+
+  return NS_OK;
 }
 
 nsresult
diff --git a/mozilla/content/base/src/nsDOMAttribute.h b/mozilla/content/base/src/nsDOMAttribute.h
index 76e23766440..8f36d313b73 100644
--- a/mozilla/content/base/src/nsDOMAttribute.h
+++ b/mozilla/content/base/src/nsDOMAttribute.h
@@ -35,9 +35,10 @@ class nsDOMAttribute;
 
 class nsIDOMAttributePrivate : public nsISupports {
 public:
-  virtual void DropReference() = 0;
-  virtual void SetContent(nsIContent* aContent) = 0;
-  virtual void SetName(const nsString& aName) = 0;
+  NS_IMETHOD DropReference() = 0;
+  NS_IMETHOD SetContent(nsIContent* aContent) = 0;
+  NS_IMETHOD GetContent(nsIContent** aContent) = 0;
+  NS_IMETHOD SetName(const nsString& aName) = 0;
 };
 
 // bogus child list for an attribute
@@ -104,9 +105,10 @@ public:
   NS_IMETHOD GetOwnerDocument(nsIDOMDocument** aOwnerDocument);
 
   // nsIDOMAttributePrivate interface
-  virtual void DropReference();
-  virtual void SetContent(nsIContent* aContent);
-  virtual void SetName(const nsString& aName);
+  NS_IMETHOD DropReference();
+  NS_IMETHOD SetContent(nsIContent* aContent);
+  NS_IMETHOD GetContent(nsIContent** aContent);
+  NS_IMETHOD SetName(const nsString& aName);
 
 private:
   nsIContent* mContent;
diff --git a/mozilla/content/base/src/nsDOMAttributeMap.cpp b/mozilla/content/base/src/nsDOMAttributeMap.cpp
index 4949b821353..35b0a1c00aa 100644
--- a/mozilla/content/base/src/nsDOMAttributeMap.cpp
+++ b/mozilla/content/base/src/nsDOMAttributeMap.cpp
@@ -23,6 +23,7 @@
 #include "nsIContent.h"
 #include "nsIDOMScriptObjectFactory.h"
 #include "nsINameSpaceManager.h"
+#include "nsDOMError.h"
 
 static NS_DEFINE_IID(kIDOMNamedNodeMapIID, NS_IDOMNAMEDNODEMAP_IID);
 static NS_DEFINE_IID(kIDOMAttrIID, NS_IDOMATTR_IID);
@@ -264,7 +265,11 @@ nsDOMAttributeMap::SetNamedItem(nsIDOMNode *aNode, nsIDOMNode **aReturn)
   nsresult result = NS_OK;
   nsIDOMAttr* attribute;
 
-  if ((nsnull != mContent) && (nsnull != aNode)) {
+  if (nsnull == aNode) {
+    return NS_ERROR_NULL_POINTER;
+  }
+
+  if (nsnull != mContent) {
     result = aNode->QueryInterface(kIDOMAttrIID, (void**)&attribute);
     if (NS_OK == result) {
       PLHashTable* attrHash;
@@ -321,26 +326,39 @@ nsDOMAttributeMap::SetNamedItem(nsIDOMNode *aNode, nsIDOMNode **aReturn)
         attribute->GetValue(value);
 
         // Associate the new attribute with the content
-        // XXX Need to fail if it's already associated with other
-        // content
         key = name.ToNewCString();
         result = attribute->QueryInterface(kIDOMAttributePrivateIID,
                                            (void **)&attrPrivate);
-        if (NS_OK == result) {
-          attrPrivate->SetContent(mContent);
-          attrPrivate->SetName(name);
+        if (NS_SUCCEEDED(result)) {
+          nsIContent* owner;
+
+          attrPrivate->GetContent(&owner);
+          if (owner) {
+            // The old attribute is already associated with another
+            // piece of content.
+            result = NS_ERROR_DOM_INUSE_ATTRIBUTE_ERR;
+            NS_RELEASE(owner);
+          }
+          else {
+            attrPrivate->SetContent(mContent);
+            attrPrivate->SetName(name);
+            NS_RELEASE(attrPrivate);
+
+            // Add the new attribute node to the hash table (maintaining
+            // a reference to it)
+            PL_HashTableAdd(attrHash, key, attribute);
+
+            // Set the attribute on the content
+            result = mContent->SetAttribute(nameSpaceID, nameAtom, value, PR_TRUE);
+            NS_IF_RELEASE(nameAtom);
+          }
           NS_RELEASE(attrPrivate);
         }
-
-        // Add the new attribute node to the hash table (maintaining
-        // a reference to it)
-        PL_HashTableAdd(attrHash, key, attribute);
-
-        // Set the attribute on the content
-        result = mContent->SetAttribute(nameSpaceID, nameAtom, value, PR_TRUE);
-        NS_IF_RELEASE(nameAtom);
       }
     }
+    else {
+      result = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+    }
   }
   else {
     *aReturn = nsnull;
@@ -400,6 +418,7 @@ nsDOMAttributeMap::RemoveNamedItem(const nsString& aName, nsIDOMNode** aReturn)
         NS_RELEASE(attribute);
       }
       else {
+        result = NS_ERROR_DOM_NOT_FOUND_ERR;
         *aReturn = nsnull;
       }
 
diff --git a/mozilla/content/base/src/nsDocument.cpp b/mozilla/content/base/src/nsDocument.cpp
index 49d153a7f4a..13bc3e67703 100644
--- a/mozilla/content/base/src/nsDocument.cpp
+++ b/mozilla/content/base/src/nsDocument.cpp
@@ -76,6 +76,7 @@
 #include "nsIDOMSelection.h"
 #include "nsIDOMRange.h"
 #include "nsIEnumerator.h"
+#include "nsDOMError.h"
 
 static NS_DEFINE_IID(kIDOMTextIID, NS_IDOMTEXT_IID);
 static NS_DEFINE_IID(kIDOMCommentIID, NS_IDOMCOMMENT_IID);
@@ -1919,7 +1920,8 @@ nsDocument::CreateElementWithNameSpace(const nsString& aTagName,
                                        const nsString& aNameSpace, 
                                        nsIDOMElement** aReturn)
 {
-  return NS_OK;
+  *aReturn = nsnull;
+  return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP    
@@ -1948,7 +1950,7 @@ nsDocument::GetNodeValue(nsString& aNodeValue)
 NS_IMETHODIMP    
 nsDocument::SetNodeValue(const nsString& aNodeValue)
 {
-  return NS_OK;
+  return NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR;
 }
 
 NS_IMETHODIMP    
@@ -2066,17 +2068,17 @@ nsDocument::InsertBefore(nsIDOMNode* aNewChild, nsIDOMNode* aRefChild, nsIDOMNod
   nsIContent *content, *refContent = nsnull;
 
   if (nsnull == aNewChild) {
-    return NS_ERROR_INVALID_ARG;
+    return NS_ERROR_NULL_POINTER;
   }
 
   aNewChild->GetNodeType(&nodeType);
   if ((COMMENT_NODE != nodeType) && (PROCESSING_INSTRUCTION_NODE != nodeType)) {
-    return NS_ERROR_INVALID_ARG;
+    return NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
   }
 
   result = aNewChild->QueryInterface(kIContentIID, (void**)&content);
   if (NS_OK != result) {
-    return result;
+    return NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
   }
 
   if (nsnull == aRefChild) {
@@ -2086,7 +2088,7 @@ nsDocument::InsertBefore(nsIDOMNode* aNewChild, nsIDOMNode* aRefChild, nsIDOMNod
     result = aRefChild->QueryInterface(kIContentIID, (void**)&refContent);
     if (NS_OK != result) {
       NS_RELEASE(content);
-      return result;
+      return NS_ERROR_DOM_NOT_FOUND_ERR;
     }
 
     if ((nsnull != mProlog) && (0 != mProlog->Count())) {
@@ -2134,23 +2136,23 @@ nsDocument::ReplaceChild(nsIDOMNode* aNewChild, nsIDOMNode* aOldChild, nsIDOMNod
   nsIContent *content, *refContent;
   
   if ((nsnull == aNewChild) || (nsnull == aOldChild)) {
-    return NS_ERROR_INVALID_ARG;
+    return NS_ERROR_NULL_POINTER;
   }
 
   aNewChild->GetNodeType(&nodeType);
   if ((COMMENT_NODE != nodeType) && (PROCESSING_INSTRUCTION_NODE != nodeType)) {
-    return NS_ERROR_INVALID_ARG;
+    return NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
   }
 
   result = aNewChild->QueryInterface(kIContentIID, (void**)&content);
   if (NS_OK != result) {
-    return result;
+    return NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
   }
 
   result = aOldChild->QueryInterface(kIContentIID, (void**)&refContent);
   if (NS_OK != result) {
     NS_RELEASE(content);
-    return result;
+    return NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
   }
 
   if ((nsnull != mProlog) && (0 != mProlog->Count())) {
@@ -2165,7 +2167,7 @@ nsDocument::ReplaceChild(nsIDOMNode* aNewChild, nsIDOMNode* aOldChild, nsIDOMNod
   }
 
   if (refContent == mRootContent) {
-    result = NS_ERROR_INVALID_ARG;
+    return NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
   }
   else if ((nsnull != mEpilog) && (0 != mEpilog->Count())) {
     index = mEpilog->IndexOf(refContent);
@@ -2203,12 +2205,12 @@ nsDocument::RemoveChild(nsIDOMNode* aOldChild, nsIDOMNode** aReturn)
   nsIContent *content;
   
   if (nsnull == aOldChild) {
-    return NS_ERROR_INVALID_ARG;
+    return NS_ERROR_NULL_POINTER;
   }
 
   result = aOldChild->QueryInterface(kIContentIID, (void**)&content);
   if (NS_OK != result) {
-    return result;
+    return NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
   }
 
   if ((nsnull != mProlog) && (0 != mProlog->Count())) {
@@ -2221,7 +2223,7 @@ nsDocument::RemoveChild(nsIDOMNode* aOldChild, nsIDOMNode** aReturn)
   }
 
   if (content == mRootContent) {
-    result = NS_ERROR_INVALID_ARG;
+    result = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
   }
   else if ((nsnull != mEpilog) && (0 != mEpilog->Count())) {
     index = mEpilog->IndexOf(content);
diff --git a/mozilla/content/base/src/nsDocumentFragment.cpp b/mozilla/content/base/src/nsDocumentFragment.cpp
index cd77d12485a..991040cd292 100644
--- a/mozilla/content/base/src/nsDocumentFragment.cpp
+++ b/mozilla/content/base/src/nsDocumentFragment.cpp
@@ -25,6 +25,7 @@
 #include "nsIDocument.h"
 #include "nsIDOMDocument.h"
 #include "nsIDOMScriptObjectFactory.h"
+#include "nsDOMError.h"
 
 
 static NS_DEFINE_IID(kIDOMDocumentFragmentIID, NS_IDOMDOCUMENTFRAGMENT_IID);
@@ -295,7 +296,8 @@ nsDocumentFragment::GetNodeValue(nsString& aNodeValue)
 NS_IMETHODIMP    
 nsDocumentFragment::SetNodeValue(const nsString& aNodeValue)
 {
-  return NS_OK;
+  // The node value can't be modified
+  return NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR;
 }
 
 NS_IMETHODIMP    
diff --git a/mozilla/content/base/src/nsGenericDOMDataNode.h b/mozilla/content/base/src/nsGenericDOMDataNode.h
index 3860c0ce188..ddddca59f93 100644
--- a/mozilla/content/base/src/nsGenericDOMDataNode.h
+++ b/mozilla/content/base/src/nsGenericDOMDataNode.h
@@ -27,6 +27,7 @@
 #include "nsVoidArray.h"
 #include "nsINameSpaceManager.h"
 #include "nsITextContent.h"
+#include "nsDOMError.h"
 
 extern const nsIID kIDOMCharacterDataIID;
 extern const nsIID kIDOMNodeIID;
@@ -77,17 +78,17 @@ struct nsGenericDOMDataNode {
   }
   nsresult    InsertBefore(nsIDOMNode* aNewChild, nsIDOMNode* aRefChild,
                            nsIDOMNode** aReturn) {
-    return NS_ERROR_FAILURE;
+    return NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR;
   }
   nsresult    ReplaceChild(nsIDOMNode* aNewChild, nsIDOMNode* aOldChild,
                            nsIDOMNode** aReturn) {
-    return NS_ERROR_FAILURE;
+    return NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR;
   }
   nsresult    RemoveChild(nsIDOMNode* aOldChild, nsIDOMNode** aReturn) {
-    return NS_ERROR_FAILURE;
+    return NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR;
   }
   nsresult    AppendChild(nsIDOMNode* aNewChild, nsIDOMNode** aReturn) {
-    return NS_ERROR_FAILURE;
+    return NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR;
   }
   nsresult    GetOwnerDocument(nsIDOMDocument** aOwnerDocument);
 
diff --git a/mozilla/content/base/src/nsGenericElement.cpp b/mozilla/content/base/src/nsGenericElement.cpp
index b05a17cadab..1d408020025 100644
--- a/mozilla/content/base/src/nsGenericElement.cpp
+++ b/mozilla/content/base/src/nsGenericElement.cpp
@@ -58,6 +58,7 @@
 #include "nsContentList.h"
 #include "prprf.h"
 #include "prmem.h"
+#include "nsDOMError.h"
 
 #include "nsLayoutAtoms.h"
 #include "nsHTMLAtoms.h"
@@ -244,7 +245,8 @@ nsGenericElement::GetNodeValue(nsString& aNodeValue)
 nsresult
 nsGenericElement::SetNodeValue(const nsString& aNodeValue)
 {
-  return NS_OK;
+  // The node value can't be modified
+  return NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR;
 }
 
 nsresult
@@ -1490,7 +1492,7 @@ nsGenericContainerElement::InsertBefore(nsIDOMNode* aNewChild,
 
   *aReturn = nsnull;
   if (nsnull == aNewChild) {
-    return NS_OK;/* XXX wrong error value */
+    return NS_ERROR_NULL_POINTER;
   }
 
   // Check if this is a document fragment. If it is, we need
@@ -1560,6 +1562,9 @@ nsGenericContainerElement::InsertBefore(nsIDOMNode* aNewChild,
       }
       NS_IF_RELEASE(refContent);
     }
+    else {
+      res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+    }
     NS_RELEASE(docFrag);
   }
   else {
@@ -1598,8 +1603,14 @@ nsGenericContainerElement::InsertBefore(nsIDOMNode* aNewChild,
               SetDocumentInChildrenOf(newContent, mDocument);
               res = InsertChildAt(newContent, pos, PR_TRUE);
             }
+            else {
+              res = NS_ERROR_DOM_NOT_FOUND_ERR;
+            }
             NS_RELEASE(refContent);
           }
+          else {
+            res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+          }
         }
       }
       NS_RELEASE(newContent);
@@ -1607,6 +1618,9 @@ nsGenericContainerElement::InsertBefore(nsIDOMNode* aNewChild,
       *aReturn = aNewChild;
       NS_ADDREF(aNewChild);
     }
+    else {
+      res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+    }
   }
 
   return res;
@@ -1619,7 +1633,10 @@ nsGenericContainerElement::ReplaceChild(nsIDOMNode* aNewChild,
 {
   *aReturn = nsnull;
   if (nsnull == aOldChild) {
-    return NS_OK;
+    return NS_ERROR_NULL_POINTER;
+  }
+  if (nsnull == aNewChild) {
+    return NS_ERROR_NULL_POINTER;
   }
   nsIContent* content = nsnull;
   nsresult res = aOldChild->QueryInterface(kIContentIID, (void**)&content);
@@ -1679,6 +1696,9 @@ nsGenericContainerElement::ReplaceChild(nsIDOMNode* aNewChild,
             }
             NS_RELEASE(docFragContent);
           }
+          else {
+            res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+          }
           NS_RELEASE(docFrag);
         }
         else {
@@ -1701,12 +1721,21 @@ nsGenericContainerElement::ReplaceChild(nsIDOMNode* aNewChild,
         }
         NS_RELEASE(newContent);
       }
+      else {
+        res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+      }
       *aReturn = aOldChild;
       NS_ADDREF(aOldChild);
     }
+    else {
+      res = NS_ERROR_DOM_NOT_FOUND_ERR;
+    }
     NS_RELEASE(content);
   }
-  
+  else {
+    res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+  }
+
   return res;
 }
 
@@ -1716,6 +1745,10 @@ nsGenericContainerElement::RemoveChild(nsIDOMNode* aOldChild,
 {
   nsIContent* content = nsnull;
   *aReturn = nsnull;
+
+  if (nsnull == aOldChild) {
+    return NS_ERROR_NULL_POINTER;
+  }
   nsresult res = aOldChild->QueryInterface(kIContentIID, (void**)&content);
   NS_ASSERTION(NS_OK == res, "Must be an nsIContent");
   if (NS_OK == res) {
@@ -1726,8 +1759,14 @@ nsGenericContainerElement::RemoveChild(nsIDOMNode* aOldChild,
       *aReturn = aOldChild;
       NS_ADDREF(aOldChild);
     }
+    else {
+      res = NS_ERROR_DOM_NOT_FOUND_ERR;
+    }
     NS_RELEASE(content);
   }
+  else {
+    res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+  }
 
   return res;
 }
diff --git a/mozilla/content/html/content/src/nsGenericHTMLElement.cpp b/mozilla/content/html/content/src/nsGenericHTMLElement.cpp
index bf63205c2c0..2c8a262b465 100644
--- a/mozilla/content/html/content/src/nsGenericHTMLElement.cpp
+++ b/mozilla/content/html/content/src/nsGenericHTMLElement.cpp
@@ -56,6 +56,7 @@
 #include "nsIView.h"
 #include "nsIViewManager.h"
 #include "nsINameSpaceManager.h"
+#include "nsDOMError.h"
 
 #include "nsIHTMLContentContainer.h"
 #include "nsHTMLParts.h"
@@ -2380,7 +2381,7 @@ nsGenericHTMLContainerElement::InsertBefore(nsIDOMNode* aNewChild,
 
   *aReturn = nsnull;
   if (nsnull == aNewChild) {
-    return NS_OK;/* XXX wrong error value */
+    return NS_ERROR_NULL_POINTER;
   }
 
   // Check if this is a document fragment. If it is, we need
@@ -2450,6 +2451,9 @@ nsGenericHTMLContainerElement::InsertBefore(nsIDOMNode* aNewChild,
       }
       NS_IF_RELEASE(refContent);
     }
+    else {
+      res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+    }
     NS_RELEASE(docFrag);
   }
   else {
@@ -2488,8 +2492,14 @@ nsGenericHTMLContainerElement::InsertBefore(nsIDOMNode* aNewChild,
               SetDocumentInChildrenOf(newContent, mDocument);
               res = InsertChildAt(newContent, pos, PR_TRUE);
             }
+            else {
+              res = NS_ERROR_DOM_NOT_FOUND_ERR;
+            }
             NS_RELEASE(refContent);
           }
+          else {
+            res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+          }
         }
       }
       NS_RELEASE(newContent);
@@ -2497,6 +2507,9 @@ nsGenericHTMLContainerElement::InsertBefore(nsIDOMNode* aNewChild,
       *aReturn = aNewChild;
       NS_ADDREF(aNewChild);
     }
+    else {
+      res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+    }
   }
 
   return res;
@@ -2509,7 +2522,7 @@ nsGenericHTMLContainerElement::ReplaceChild(nsIDOMNode* aNewChild,
 {
   *aReturn = nsnull;
   if (nsnull == aOldChild) {
-    return NS_OK;
+    return NS_ERROR_NULL_POINTER;
   }
   if (nsnull == aNewChild) {
     return NS_ERROR_NULL_POINTER;
@@ -2522,7 +2535,7 @@ nsGenericHTMLContainerElement::ReplaceChild(nsIDOMNode* aNewChild,
     IndexOf(content, pos);
     if (pos >= 0) {
       nsIContent* newContent = nsnull;
-      res = aNewChild->QueryInterface(kIContentIID, (void**)&newContent);
+      nsresult res = aNewChild->QueryInterface(kIContentIID, (void**)&newContent);
       NS_ASSERTION(NS_OK == res, "Must be an nsIContent");
       if (NS_OK == res) {
         // Check if this is a document fragment. If it is, we need
@@ -2572,6 +2585,9 @@ nsGenericHTMLContainerElement::ReplaceChild(nsIDOMNode* aNewChild,
             }
             NS_RELEASE(docFragContent);
           }
+          else {
+            res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+          }
           NS_RELEASE(docFrag);
         }
         else {
@@ -2587,19 +2603,28 @@ nsGenericHTMLContainerElement::ReplaceChild(nsIDOMNode* aNewChild,
               }
               NS_RELEASE(oldParent);
             }
-
+           
             SetDocumentInChildrenOf(newContent, mDocument);
             res = ReplaceChildAt(newContent, pos, PR_TRUE);
           }
         }
         NS_RELEASE(newContent);
       }
+      else {
+        res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+      }
       *aReturn = aOldChild;
       NS_ADDREF(aOldChild);
     }
+    else {
+      res = NS_ERROR_DOM_NOT_FOUND_ERR;
+    }
     NS_RELEASE(content);
   }
-  
+  else {
+    res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+  }
+
   return res;
 }
 
@@ -2607,15 +2632,15 @@ nsresult
 nsGenericHTMLContainerElement::RemoveChild(nsIDOMNode* aOldChild, 
                                            nsIDOMNode** aReturn)
 {
-  *aReturn = nsnull;
-  if (nsnull == aOldChild) {
-    return NS_OK;
-  }
-
   nsIContent* content = nsnull;
+  *aReturn = nsnull;
+
+  if (nsnull == aOldChild) {
+    return NS_ERROR_NULL_POINTER;
+  }
   nsresult res = aOldChild->QueryInterface(kIContentIID, (void**)&content);
   NS_ASSERTION(NS_OK == res, "Must be an nsIContent");
-  if (NS_SUCCEEDED(res)) {
+  if (NS_OK == res) {
     PRInt32 pos;
     IndexOf(content, pos);
     if (pos >= 0) {
@@ -2623,8 +2648,15 @@ nsGenericHTMLContainerElement::RemoveChild(nsIDOMNode* aOldChild,
       *aReturn = aOldChild;
       NS_ADDREF(aOldChild);
     }
+    else {
+      res = NS_ERROR_DOM_NOT_FOUND_ERR;
+    }
     NS_RELEASE(content);
   }
+  else {
+    res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+  }
+
   return res;
 }
 
diff --git a/mozilla/content/html/document/src/nsHTMLDocument.cpp b/mozilla/content/html/document/src/nsHTMLDocument.cpp
index 1963d5956b1..04d47dca279 100644
--- a/mozilla/content/html/document/src/nsHTMLDocument.cpp
+++ b/mozilla/content/html/document/src/nsHTMLDocument.cpp
@@ -57,6 +57,7 @@
 #include "CNavDTD.h"
 #include "nsIScriptGlobalObject.h"
 #include "nsContentList.h"
+#include "nsDOMError.h"
 
 #ifndef NECKO
 #include "nsINetService.h"
@@ -1010,7 +1011,7 @@ nsHTMLDocument::CreateProcessingInstruction(const nsString& aTarget,
   // There are no PIs for HTML
   *aReturn = nsnull;
   
-  return NS_OK;
+  return NS_ERROR_DOM_NOT_SUPPORTED_ERR;
 }
 
 NS_IMETHODIMP    
@@ -1020,7 +1021,7 @@ nsHTMLDocument::CreateCDATASection(const nsString& aData,
   // There are no CDATASections in HTML
   *aReturn = nsnull;
 
-  return NS_OK;
+  return NS_ERROR_DOM_NOT_SUPPORTED_ERR;
 }
  
 NS_IMETHODIMP    
@@ -1030,7 +1031,7 @@ nsHTMLDocument::CreateEntityReference(const nsString& aName,
   // There are no EntityReferences in HTML
   *aReturn = nsnull;
 
-  return NS_OK;
+  return NS_ERROR_DOM_NOT_SUPPORTED_ERR;
 }
 
 
diff --git a/mozilla/layout/base/src/nsDOMAttribute.cpp b/mozilla/layout/base/src/nsDOMAttribute.cpp
index 05f315b7d8b..b93e22e2b4c 100644
--- a/mozilla/layout/base/src/nsDOMAttribute.cpp
+++ b/mozilla/layout/base/src/nsDOMAttribute.cpp
@@ -94,22 +94,37 @@ nsDOMAttribute::QueryInterface(REFNSIID aIID, void** aInstancePtr)
 NS_IMPL_ADDREF(nsDOMAttribute)
 NS_IMPL_RELEASE(nsDOMAttribute)
 
-void 
+NS_IMETHODIMP
 nsDOMAttribute::DropReference()
 {
   mContent = nsnull;
+
+  return NS_OK;
 }
 
-void 
+NS_IMETHODIMP
 nsDOMAttribute::SetContent(nsIContent* aContent)
 {
   mContent = aContent;
+
+  return NS_OK;
 }
 
-void 
+NS_IMETHODIMP
+nsDOMAttribute::GetContent(nsIContent** aContent)
+{
+  *aContent = mContent;
+  NS_IF_ADDREF(mContent);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
 nsDOMAttribute::SetName(const nsString& aName)
 {
   mName=aName;
+
+  return NS_OK;
 }
 
 nsresult
diff --git a/mozilla/layout/base/src/nsDOMAttribute.h b/mozilla/layout/base/src/nsDOMAttribute.h
index 76e23766440..8f36d313b73 100644
--- a/mozilla/layout/base/src/nsDOMAttribute.h
+++ b/mozilla/layout/base/src/nsDOMAttribute.h
@@ -35,9 +35,10 @@ class nsDOMAttribute;
 
 class nsIDOMAttributePrivate : public nsISupports {
 public:
-  virtual void DropReference() = 0;
-  virtual void SetContent(nsIContent* aContent) = 0;
-  virtual void SetName(const nsString& aName) = 0;
+  NS_IMETHOD DropReference() = 0;
+  NS_IMETHOD SetContent(nsIContent* aContent) = 0;
+  NS_IMETHOD GetContent(nsIContent** aContent) = 0;
+  NS_IMETHOD SetName(const nsString& aName) = 0;
 };
 
 // bogus child list for an attribute
@@ -104,9 +105,10 @@ public:
   NS_IMETHOD GetOwnerDocument(nsIDOMDocument** aOwnerDocument);
 
   // nsIDOMAttributePrivate interface
-  virtual void DropReference();
-  virtual void SetContent(nsIContent* aContent);
-  virtual void SetName(const nsString& aName);
+  NS_IMETHOD DropReference();
+  NS_IMETHOD SetContent(nsIContent* aContent);
+  NS_IMETHOD GetContent(nsIContent** aContent);
+  NS_IMETHOD SetName(const nsString& aName);
 
 private:
   nsIContent* mContent;
diff --git a/mozilla/layout/base/src/nsDOMAttributeMap.cpp b/mozilla/layout/base/src/nsDOMAttributeMap.cpp
index 4949b821353..35b0a1c00aa 100644
--- a/mozilla/layout/base/src/nsDOMAttributeMap.cpp
+++ b/mozilla/layout/base/src/nsDOMAttributeMap.cpp
@@ -23,6 +23,7 @@
 #include "nsIContent.h"
 #include "nsIDOMScriptObjectFactory.h"
 #include "nsINameSpaceManager.h"
+#include "nsDOMError.h"
 
 static NS_DEFINE_IID(kIDOMNamedNodeMapIID, NS_IDOMNAMEDNODEMAP_IID);
 static NS_DEFINE_IID(kIDOMAttrIID, NS_IDOMATTR_IID);
@@ -264,7 +265,11 @@ nsDOMAttributeMap::SetNamedItem(nsIDOMNode *aNode, nsIDOMNode **aReturn)
   nsresult result = NS_OK;
   nsIDOMAttr* attribute;
 
-  if ((nsnull != mContent) && (nsnull != aNode)) {
+  if (nsnull == aNode) {
+    return NS_ERROR_NULL_POINTER;
+  }
+
+  if (nsnull != mContent) {
     result = aNode->QueryInterface(kIDOMAttrIID, (void**)&attribute);
     if (NS_OK == result) {
       PLHashTable* attrHash;
@@ -321,26 +326,39 @@ nsDOMAttributeMap::SetNamedItem(nsIDOMNode *aNode, nsIDOMNode **aReturn)
         attribute->GetValue(value);
 
         // Associate the new attribute with the content
-        // XXX Need to fail if it's already associated with other
-        // content
         key = name.ToNewCString();
         result = attribute->QueryInterface(kIDOMAttributePrivateIID,
                                            (void **)&attrPrivate);
-        if (NS_OK == result) {
-          attrPrivate->SetContent(mContent);
-          attrPrivate->SetName(name);
+        if (NS_SUCCEEDED(result)) {
+          nsIContent* owner;
+
+          attrPrivate->GetContent(&owner);
+          if (owner) {
+            // The old attribute is already associated with another
+            // piece of content.
+            result = NS_ERROR_DOM_INUSE_ATTRIBUTE_ERR;
+            NS_RELEASE(owner);
+          }
+          else {
+            attrPrivate->SetContent(mContent);
+            attrPrivate->SetName(name);
+            NS_RELEASE(attrPrivate);
+
+            // Add the new attribute node to the hash table (maintaining
+            // a reference to it)
+            PL_HashTableAdd(attrHash, key, attribute);
+
+            // Set the attribute on the content
+            result = mContent->SetAttribute(nameSpaceID, nameAtom, value, PR_TRUE);
+            NS_IF_RELEASE(nameAtom);
+          }
           NS_RELEASE(attrPrivate);
         }
-
-        // Add the new attribute node to the hash table (maintaining
-        // a reference to it)
-        PL_HashTableAdd(attrHash, key, attribute);
-
-        // Set the attribute on the content
-        result = mContent->SetAttribute(nameSpaceID, nameAtom, value, PR_TRUE);
-        NS_IF_RELEASE(nameAtom);
       }
     }
+    else {
+      result = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+    }
   }
   else {
     *aReturn = nsnull;
@@ -400,6 +418,7 @@ nsDOMAttributeMap::RemoveNamedItem(const nsString& aName, nsIDOMNode** aReturn)
         NS_RELEASE(attribute);
       }
       else {
+        result = NS_ERROR_DOM_NOT_FOUND_ERR;
         *aReturn = nsnull;
       }
 
diff --git a/mozilla/layout/base/src/nsDocument.cpp b/mozilla/layout/base/src/nsDocument.cpp
index 49d153a7f4a..13bc3e67703 100644
--- a/mozilla/layout/base/src/nsDocument.cpp
+++ b/mozilla/layout/base/src/nsDocument.cpp
@@ -76,6 +76,7 @@
 #include "nsIDOMSelection.h"
 #include "nsIDOMRange.h"
 #include "nsIEnumerator.h"
+#include "nsDOMError.h"
 
 static NS_DEFINE_IID(kIDOMTextIID, NS_IDOMTEXT_IID);
 static NS_DEFINE_IID(kIDOMCommentIID, NS_IDOMCOMMENT_IID);
@@ -1919,7 +1920,8 @@ nsDocument::CreateElementWithNameSpace(const nsString& aTagName,
                                        const nsString& aNameSpace, 
                                        nsIDOMElement** aReturn)
 {
-  return NS_OK;
+  *aReturn = nsnull;
+  return NS_ERROR_NOT_IMPLEMENTED;
 }
 
 NS_IMETHODIMP    
@@ -1948,7 +1950,7 @@ nsDocument::GetNodeValue(nsString& aNodeValue)
 NS_IMETHODIMP    
 nsDocument::SetNodeValue(const nsString& aNodeValue)
 {
-  return NS_OK;
+  return NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR;
 }
 
 NS_IMETHODIMP    
@@ -2066,17 +2068,17 @@ nsDocument::InsertBefore(nsIDOMNode* aNewChild, nsIDOMNode* aRefChild, nsIDOMNod
   nsIContent *content, *refContent = nsnull;
 
   if (nsnull == aNewChild) {
-    return NS_ERROR_INVALID_ARG;
+    return NS_ERROR_NULL_POINTER;
   }
 
   aNewChild->GetNodeType(&nodeType);
   if ((COMMENT_NODE != nodeType) && (PROCESSING_INSTRUCTION_NODE != nodeType)) {
-    return NS_ERROR_INVALID_ARG;
+    return NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
   }
 
   result = aNewChild->QueryInterface(kIContentIID, (void**)&content);
   if (NS_OK != result) {
-    return result;
+    return NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
   }
 
   if (nsnull == aRefChild) {
@@ -2086,7 +2088,7 @@ nsDocument::InsertBefore(nsIDOMNode* aNewChild, nsIDOMNode* aRefChild, nsIDOMNod
     result = aRefChild->QueryInterface(kIContentIID, (void**)&refContent);
     if (NS_OK != result) {
       NS_RELEASE(content);
-      return result;
+      return NS_ERROR_DOM_NOT_FOUND_ERR;
     }
 
     if ((nsnull != mProlog) && (0 != mProlog->Count())) {
@@ -2134,23 +2136,23 @@ nsDocument::ReplaceChild(nsIDOMNode* aNewChild, nsIDOMNode* aOldChild, nsIDOMNod
   nsIContent *content, *refContent;
   
   if ((nsnull == aNewChild) || (nsnull == aOldChild)) {
-    return NS_ERROR_INVALID_ARG;
+    return NS_ERROR_NULL_POINTER;
   }
 
   aNewChild->GetNodeType(&nodeType);
   if ((COMMENT_NODE != nodeType) && (PROCESSING_INSTRUCTION_NODE != nodeType)) {
-    return NS_ERROR_INVALID_ARG;
+    return NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
   }
 
   result = aNewChild->QueryInterface(kIContentIID, (void**)&content);
   if (NS_OK != result) {
-    return result;
+    return NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
   }
 
   result = aOldChild->QueryInterface(kIContentIID, (void**)&refContent);
   if (NS_OK != result) {
     NS_RELEASE(content);
-    return result;
+    return NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
   }
 
   if ((nsnull != mProlog) && (0 != mProlog->Count())) {
@@ -2165,7 +2167,7 @@ nsDocument::ReplaceChild(nsIDOMNode* aNewChild, nsIDOMNode* aOldChild, nsIDOMNod
   }
 
   if (refContent == mRootContent) {
-    result = NS_ERROR_INVALID_ARG;
+    return NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
   }
   else if ((nsnull != mEpilog) && (0 != mEpilog->Count())) {
     index = mEpilog->IndexOf(refContent);
@@ -2203,12 +2205,12 @@ nsDocument::RemoveChild(nsIDOMNode* aOldChild, nsIDOMNode** aReturn)
   nsIContent *content;
   
   if (nsnull == aOldChild) {
-    return NS_ERROR_INVALID_ARG;
+    return NS_ERROR_NULL_POINTER;
   }
 
   result = aOldChild->QueryInterface(kIContentIID, (void**)&content);
   if (NS_OK != result) {
-    return result;
+    return NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
   }
 
   if ((nsnull != mProlog) && (0 != mProlog->Count())) {
@@ -2221,7 +2223,7 @@ nsDocument::RemoveChild(nsIDOMNode* aOldChild, nsIDOMNode** aReturn)
   }
 
   if (content == mRootContent) {
-    result = NS_ERROR_INVALID_ARG;
+    result = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
   }
   else if ((nsnull != mEpilog) && (0 != mEpilog->Count())) {
     index = mEpilog->IndexOf(content);
diff --git a/mozilla/layout/base/src/nsDocumentFragment.cpp b/mozilla/layout/base/src/nsDocumentFragment.cpp
index cd77d12485a..991040cd292 100644
--- a/mozilla/layout/base/src/nsDocumentFragment.cpp
+++ b/mozilla/layout/base/src/nsDocumentFragment.cpp
@@ -25,6 +25,7 @@
 #include "nsIDocument.h"
 #include "nsIDOMDocument.h"
 #include "nsIDOMScriptObjectFactory.h"
+#include "nsDOMError.h"
 
 
 static NS_DEFINE_IID(kIDOMDocumentFragmentIID, NS_IDOMDOCUMENTFRAGMENT_IID);
@@ -295,7 +296,8 @@ nsDocumentFragment::GetNodeValue(nsString& aNodeValue)
 NS_IMETHODIMP    
 nsDocumentFragment::SetNodeValue(const nsString& aNodeValue)
 {
-  return NS_OK;
+  // The node value can't be modified
+  return NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR;
 }
 
 NS_IMETHODIMP    
diff --git a/mozilla/layout/base/src/nsGenericDOMDataNode.h b/mozilla/layout/base/src/nsGenericDOMDataNode.h
index 3860c0ce188..ddddca59f93 100644
--- a/mozilla/layout/base/src/nsGenericDOMDataNode.h
+++ b/mozilla/layout/base/src/nsGenericDOMDataNode.h
@@ -27,6 +27,7 @@
 #include "nsVoidArray.h"
 #include "nsINameSpaceManager.h"
 #include "nsITextContent.h"
+#include "nsDOMError.h"
 
 extern const nsIID kIDOMCharacterDataIID;
 extern const nsIID kIDOMNodeIID;
@@ -77,17 +78,17 @@ struct nsGenericDOMDataNode {
   }
   nsresult    InsertBefore(nsIDOMNode* aNewChild, nsIDOMNode* aRefChild,
                            nsIDOMNode** aReturn) {
-    return NS_ERROR_FAILURE;
+    return NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR;
   }
   nsresult    ReplaceChild(nsIDOMNode* aNewChild, nsIDOMNode* aOldChild,
                            nsIDOMNode** aReturn) {
-    return NS_ERROR_FAILURE;
+    return NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR;
   }
   nsresult    RemoveChild(nsIDOMNode* aOldChild, nsIDOMNode** aReturn) {
-    return NS_ERROR_FAILURE;
+    return NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR;
   }
   nsresult    AppendChild(nsIDOMNode* aNewChild, nsIDOMNode** aReturn) {
-    return NS_ERROR_FAILURE;
+    return NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR;
   }
   nsresult    GetOwnerDocument(nsIDOMDocument** aOwnerDocument);
 
diff --git a/mozilla/layout/base/src/nsGenericElement.cpp b/mozilla/layout/base/src/nsGenericElement.cpp
index b05a17cadab..1d408020025 100644
--- a/mozilla/layout/base/src/nsGenericElement.cpp
+++ b/mozilla/layout/base/src/nsGenericElement.cpp
@@ -58,6 +58,7 @@
 #include "nsContentList.h"
 #include "prprf.h"
 #include "prmem.h"
+#include "nsDOMError.h"
 
 #include "nsLayoutAtoms.h"
 #include "nsHTMLAtoms.h"
@@ -244,7 +245,8 @@ nsGenericElement::GetNodeValue(nsString& aNodeValue)
 nsresult
 nsGenericElement::SetNodeValue(const nsString& aNodeValue)
 {
-  return NS_OK;
+  // The node value can't be modified
+  return NS_ERROR_DOM_NO_MODIFICATION_ALLOWED_ERR;
 }
 
 nsresult
@@ -1490,7 +1492,7 @@ nsGenericContainerElement::InsertBefore(nsIDOMNode* aNewChild,
 
   *aReturn = nsnull;
   if (nsnull == aNewChild) {
-    return NS_OK;/* XXX wrong error value */
+    return NS_ERROR_NULL_POINTER;
   }
 
   // Check if this is a document fragment. If it is, we need
@@ -1560,6 +1562,9 @@ nsGenericContainerElement::InsertBefore(nsIDOMNode* aNewChild,
       }
       NS_IF_RELEASE(refContent);
     }
+    else {
+      res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+    }
     NS_RELEASE(docFrag);
   }
   else {
@@ -1598,8 +1603,14 @@ nsGenericContainerElement::InsertBefore(nsIDOMNode* aNewChild,
               SetDocumentInChildrenOf(newContent, mDocument);
               res = InsertChildAt(newContent, pos, PR_TRUE);
             }
+            else {
+              res = NS_ERROR_DOM_NOT_FOUND_ERR;
+            }
             NS_RELEASE(refContent);
           }
+          else {
+            res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+          }
         }
       }
       NS_RELEASE(newContent);
@@ -1607,6 +1618,9 @@ nsGenericContainerElement::InsertBefore(nsIDOMNode* aNewChild,
       *aReturn = aNewChild;
       NS_ADDREF(aNewChild);
     }
+    else {
+      res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+    }
   }
 
   return res;
@@ -1619,7 +1633,10 @@ nsGenericContainerElement::ReplaceChild(nsIDOMNode* aNewChild,
 {
   *aReturn = nsnull;
   if (nsnull == aOldChild) {
-    return NS_OK;
+    return NS_ERROR_NULL_POINTER;
+  }
+  if (nsnull == aNewChild) {
+    return NS_ERROR_NULL_POINTER;
   }
   nsIContent* content = nsnull;
   nsresult res = aOldChild->QueryInterface(kIContentIID, (void**)&content);
@@ -1679,6 +1696,9 @@ nsGenericContainerElement::ReplaceChild(nsIDOMNode* aNewChild,
             }
             NS_RELEASE(docFragContent);
           }
+          else {
+            res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+          }
           NS_RELEASE(docFrag);
         }
         else {
@@ -1701,12 +1721,21 @@ nsGenericContainerElement::ReplaceChild(nsIDOMNode* aNewChild,
         }
         NS_RELEASE(newContent);
       }
+      else {
+        res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+      }
       *aReturn = aOldChild;
       NS_ADDREF(aOldChild);
     }
+    else {
+      res = NS_ERROR_DOM_NOT_FOUND_ERR;
+    }
     NS_RELEASE(content);
   }
-  
+  else {
+    res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+  }
+
   return res;
 }
 
@@ -1716,6 +1745,10 @@ nsGenericContainerElement::RemoveChild(nsIDOMNode* aOldChild,
 {
   nsIContent* content = nsnull;
   *aReturn = nsnull;
+
+  if (nsnull == aOldChild) {
+    return NS_ERROR_NULL_POINTER;
+  }
   nsresult res = aOldChild->QueryInterface(kIContentIID, (void**)&content);
   NS_ASSERTION(NS_OK == res, "Must be an nsIContent");
   if (NS_OK == res) {
@@ -1726,8 +1759,14 @@ nsGenericContainerElement::RemoveChild(nsIDOMNode* aOldChild,
       *aReturn = aOldChild;
       NS_ADDREF(aOldChild);
     }
+    else {
+      res = NS_ERROR_DOM_NOT_FOUND_ERR;
+    }
     NS_RELEASE(content);
   }
+  else {
+    res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+  }
 
   return res;
 }
diff --git a/mozilla/layout/html/content/src/nsGenericHTMLElement.cpp b/mozilla/layout/html/content/src/nsGenericHTMLElement.cpp
index bf63205c2c0..2c8a262b465 100644
--- a/mozilla/layout/html/content/src/nsGenericHTMLElement.cpp
+++ b/mozilla/layout/html/content/src/nsGenericHTMLElement.cpp
@@ -56,6 +56,7 @@
 #include "nsIView.h"
 #include "nsIViewManager.h"
 #include "nsINameSpaceManager.h"
+#include "nsDOMError.h"
 
 #include "nsIHTMLContentContainer.h"
 #include "nsHTMLParts.h"
@@ -2380,7 +2381,7 @@ nsGenericHTMLContainerElement::InsertBefore(nsIDOMNode* aNewChild,
 
   *aReturn = nsnull;
   if (nsnull == aNewChild) {
-    return NS_OK;/* XXX wrong error value */
+    return NS_ERROR_NULL_POINTER;
   }
 
   // Check if this is a document fragment. If it is, we need
@@ -2450,6 +2451,9 @@ nsGenericHTMLContainerElement::InsertBefore(nsIDOMNode* aNewChild,
       }
       NS_IF_RELEASE(refContent);
     }
+    else {
+      res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+    }
     NS_RELEASE(docFrag);
   }
   else {
@@ -2488,8 +2492,14 @@ nsGenericHTMLContainerElement::InsertBefore(nsIDOMNode* aNewChild,
               SetDocumentInChildrenOf(newContent, mDocument);
               res = InsertChildAt(newContent, pos, PR_TRUE);
             }
+            else {
+              res = NS_ERROR_DOM_NOT_FOUND_ERR;
+            }
             NS_RELEASE(refContent);
           }
+          else {
+            res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+          }
         }
       }
       NS_RELEASE(newContent);
@@ -2497,6 +2507,9 @@ nsGenericHTMLContainerElement::InsertBefore(nsIDOMNode* aNewChild,
       *aReturn = aNewChild;
       NS_ADDREF(aNewChild);
     }
+    else {
+      res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+    }
   }
 
   return res;
@@ -2509,7 +2522,7 @@ nsGenericHTMLContainerElement::ReplaceChild(nsIDOMNode* aNewChild,
 {
   *aReturn = nsnull;
   if (nsnull == aOldChild) {
-    return NS_OK;
+    return NS_ERROR_NULL_POINTER;
   }
   if (nsnull == aNewChild) {
     return NS_ERROR_NULL_POINTER;
@@ -2522,7 +2535,7 @@ nsGenericHTMLContainerElement::ReplaceChild(nsIDOMNode* aNewChild,
     IndexOf(content, pos);
     if (pos >= 0) {
       nsIContent* newContent = nsnull;
-      res = aNewChild->QueryInterface(kIContentIID, (void**)&newContent);
+      nsresult res = aNewChild->QueryInterface(kIContentIID, (void**)&newContent);
       NS_ASSERTION(NS_OK == res, "Must be an nsIContent");
       if (NS_OK == res) {
         // Check if this is a document fragment. If it is, we need
@@ -2572,6 +2585,9 @@ nsGenericHTMLContainerElement::ReplaceChild(nsIDOMNode* aNewChild,
             }
             NS_RELEASE(docFragContent);
           }
+          else {
+            res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+          }
           NS_RELEASE(docFrag);
         }
         else {
@@ -2587,19 +2603,28 @@ nsGenericHTMLContainerElement::ReplaceChild(nsIDOMNode* aNewChild,
               }
               NS_RELEASE(oldParent);
             }
-
+           
             SetDocumentInChildrenOf(newContent, mDocument);
             res = ReplaceChildAt(newContent, pos, PR_TRUE);
           }
         }
         NS_RELEASE(newContent);
       }
+      else {
+        res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+      }
       *aReturn = aOldChild;
       NS_ADDREF(aOldChild);
     }
+    else {
+      res = NS_ERROR_DOM_NOT_FOUND_ERR;
+    }
     NS_RELEASE(content);
   }
-  
+  else {
+    res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+  }
+
   return res;
 }
 
@@ -2607,15 +2632,15 @@ nsresult
 nsGenericHTMLContainerElement::RemoveChild(nsIDOMNode* aOldChild, 
                                            nsIDOMNode** aReturn)
 {
-  *aReturn = nsnull;
-  if (nsnull == aOldChild) {
-    return NS_OK;
-  }
-
   nsIContent* content = nsnull;
+  *aReturn = nsnull;
+
+  if (nsnull == aOldChild) {
+    return NS_ERROR_NULL_POINTER;
+  }
   nsresult res = aOldChild->QueryInterface(kIContentIID, (void**)&content);
   NS_ASSERTION(NS_OK == res, "Must be an nsIContent");
-  if (NS_SUCCEEDED(res)) {
+  if (NS_OK == res) {
     PRInt32 pos;
     IndexOf(content, pos);
     if (pos >= 0) {
@@ -2623,8 +2648,15 @@ nsGenericHTMLContainerElement::RemoveChild(nsIDOMNode* aOldChild,
       *aReturn = aOldChild;
       NS_ADDREF(aOldChild);
     }
+    else {
+      res = NS_ERROR_DOM_NOT_FOUND_ERR;
+    }
     NS_RELEASE(content);
   }
+  else {
+    res = NS_ERROR_DOM_HIERARCHY_REQUEST_ERR;
+  }
+
   return res;
 }
 
diff --git a/mozilla/layout/html/document/src/nsHTMLDocument.cpp b/mozilla/layout/html/document/src/nsHTMLDocument.cpp
index 1963d5956b1..04d47dca279 100644
--- a/mozilla/layout/html/document/src/nsHTMLDocument.cpp
+++ b/mozilla/layout/html/document/src/nsHTMLDocument.cpp
@@ -57,6 +57,7 @@
 #include "CNavDTD.h"
 #include "nsIScriptGlobalObject.h"
 #include "nsContentList.h"
+#include "nsDOMError.h"
 
 #ifndef NECKO
 #include "nsINetService.h"
@@ -1010,7 +1011,7 @@ nsHTMLDocument::CreateProcessingInstruction(const nsString& aTarget,
   // There are no PIs for HTML
   *aReturn = nsnull;
   
-  return NS_OK;
+  return NS_ERROR_DOM_NOT_SUPPORTED_ERR;
 }
 
 NS_IMETHODIMP    
@@ -1020,7 +1021,7 @@ nsHTMLDocument::CreateCDATASection(const nsString& aData,
   // There are no CDATASections in HTML
   *aReturn = nsnull;
 
-  return NS_OK;
+  return NS_ERROR_DOM_NOT_SUPPORTED_ERR;
 }
  
 NS_IMETHODIMP    
@@ -1030,7 +1031,7 @@ nsHTMLDocument::CreateEntityReference(const nsString& aName,
   // There are no EntityReferences in HTML
   *aReturn = nsnull;
 
-  return NS_OK;
+  return NS_ERROR_DOM_NOT_SUPPORTED_ERR;
 }