diff --git a/content/xul/content/src/nsXULElement.cpp b/content/xul/content/src/nsXULElement.cpp
index 864507347ac..5f82f2aa664 100644
--- a/content/xul/content/src/nsXULElement.cpp
+++ b/content/xul/content/src/nsXULElement.cpp
@@ -2717,14 +2717,15 @@ nsXULElement::HandleDOMEvent(nsIPresContext* aPresContext,
 NS_IMETHODIMP
 nsXULElement::GetContentID(PRUint32* aID)
 {
-    *aID = 0;
-    return NS_ERROR_NOT_IMPLEMENTED;
+    *aID = mContentId;
+    return NS_OK;
 }
 
 NS_IMETHODIMP
 nsXULElement::SetContentID(PRUint32 aID)
 {
-    return NS_ERROR_NOT_IMPLEMENTED;
+    mContentId = aID;
+    return NS_OK;
 }
 
 NS_IMETHODIMP 
diff --git a/content/xul/content/src/nsXULElement.h b/content/xul/content/src/nsXULElement.h
index bc229b04f68..5b7e6dc2b39 100644
--- a/content/xul/content/src/nsXULElement.h
+++ b/content/xul/content/src/nsXULElement.h
@@ -519,6 +519,7 @@ protected:
     nsCOMPtr<nsISupportsArray>          mChildren;           // [OWNER]
     nsCOMPtr<nsIEventListenerManager>   mListenerManager;    // [OWNER]
     void*                               mScriptObject;       // [OWNER]
+    PRInt32                             mContentId;
 
     // The state of our sloth for lazy content model construction via
     // RDF; see nsIXULContent and nsRDFGenericBuilder.
diff --git a/content/xul/document/src/nsXULDocument.cpp b/content/xul/document/src/nsXULDocument.cpp
index 56121d61b9a..fb9f140a826 100644
--- a/content/xul/document/src/nsXULDocument.cpp
+++ b/content/xul/document/src/nsXULDocument.cpp
@@ -55,6 +55,7 @@
 #include "nsIBrowserWindow.h"
 #include "nsIChromeRegistry.h"
 #include "nsIComponentManager.h"
+#include "nsIContentSink.h" // for NS_CONTENT_ID_COUNTER_BASE
 #include "nsIContentViewer.h"
 #include "nsICSSStyleSheet.h"
 #include "nsIDOMEvent.h"
@@ -203,7 +204,6 @@ nsIXULPrototypeCache* nsXULDocument::gXULCache;
 
 PRLogModuleInfo* nsXULDocument::gXULLog;
 
-
 //----------------------------------------------------------------------
 //
 // PlaceholderChannel
@@ -310,6 +310,7 @@ nsXULDocument::nsXULDocument(void)
       mDisplaySelection(PR_FALSE),
       mIsPopup(PR_FALSE),
       mResolutionPhase(nsForwardReference::eStart),
+      mNextContentID(NS_CONTENT_ID_COUNTER_BASE),
       mState(eState_Master),
       mCurrentScriptProto(nsnull)
 {
@@ -3886,8 +3887,8 @@ nsXULDocument::RebuildWidgetItem(nsIContent* aElement)
 
 nsresult
 nsXULDocument::CreateElement(PRInt32 aNameSpaceID,
-                               nsIAtom* aTag,
-                               nsIContent** aResult)
+                             nsIAtom* aTag,
+                             nsIContent** aResult)
 {
     nsresult rv;
     nsCOMPtr<nsIContent> result;
@@ -3913,6 +3914,8 @@ nsXULDocument::CreateElement(PRInt32 aNameSpaceID,
     NS_ASSERTION(NS_SUCCEEDED(rv), "unable to set element's document");
     if (NS_FAILED(rv)) return rv;
 
+    result->SetContentID(mNextContentID++);
+
     *aResult = result;
     NS_ADDREF(*aResult);
     return NS_OK;
@@ -4941,6 +4944,8 @@ nsXULDocument::CreateElement(nsXULPrototypeElement* aPrototype, nsIContent** aRe
         }
     }
 
+    result->SetContentID(mNextContentID++);
+
     *aResult = result;
     NS_ADDREF(*aResult);
     return NS_OK;
diff --git a/content/xul/document/src/nsXULDocument.h b/content/xul/document/src/nsXULDocument.h
index 313c478f0fd..1bfb50ddca9 100644
--- a/content/xul/document/src/nsXULDocument.h
+++ b/content/xul/document/src/nsXULDocument.h
@@ -525,6 +525,7 @@ protected:
 
     nsVoidArray mForwardReferences;
     nsForwardReference::Phase mResolutionPhase;
+    PRInt32 mNextContentID;
 
     // The following are pointers into the content model which provide access to
     // the objects triggering either a popup or a tooltip. These are marked as
diff --git a/rdf/content/src/nsXULDocument.cpp b/rdf/content/src/nsXULDocument.cpp
index 56121d61b9a..fb9f140a826 100644
--- a/rdf/content/src/nsXULDocument.cpp
+++ b/rdf/content/src/nsXULDocument.cpp
@@ -55,6 +55,7 @@
 #include "nsIBrowserWindow.h"
 #include "nsIChromeRegistry.h"
 #include "nsIComponentManager.h"
+#include "nsIContentSink.h" // for NS_CONTENT_ID_COUNTER_BASE
 #include "nsIContentViewer.h"
 #include "nsICSSStyleSheet.h"
 #include "nsIDOMEvent.h"
@@ -203,7 +204,6 @@ nsIXULPrototypeCache* nsXULDocument::gXULCache;
 
 PRLogModuleInfo* nsXULDocument::gXULLog;
 
-
 //----------------------------------------------------------------------
 //
 // PlaceholderChannel
@@ -310,6 +310,7 @@ nsXULDocument::nsXULDocument(void)
       mDisplaySelection(PR_FALSE),
       mIsPopup(PR_FALSE),
       mResolutionPhase(nsForwardReference::eStart),
+      mNextContentID(NS_CONTENT_ID_COUNTER_BASE),
       mState(eState_Master),
       mCurrentScriptProto(nsnull)
 {
@@ -3886,8 +3887,8 @@ nsXULDocument::RebuildWidgetItem(nsIContent* aElement)
 
 nsresult
 nsXULDocument::CreateElement(PRInt32 aNameSpaceID,
-                               nsIAtom* aTag,
-                               nsIContent** aResult)
+                             nsIAtom* aTag,
+                             nsIContent** aResult)
 {
     nsresult rv;
     nsCOMPtr<nsIContent> result;
@@ -3913,6 +3914,8 @@ nsXULDocument::CreateElement(PRInt32 aNameSpaceID,
     NS_ASSERTION(NS_SUCCEEDED(rv), "unable to set element's document");
     if (NS_FAILED(rv)) return rv;
 
+    result->SetContentID(mNextContentID++);
+
     *aResult = result;
     NS_ADDREF(*aResult);
     return NS_OK;
@@ -4941,6 +4944,8 @@ nsXULDocument::CreateElement(nsXULPrototypeElement* aPrototype, nsIContent** aRe
         }
     }
 
+    result->SetContentID(mNextContentID++);
+
     *aResult = result;
     NS_ADDREF(*aResult);
     return NS_OK;
diff --git a/rdf/content/src/nsXULDocument.h b/rdf/content/src/nsXULDocument.h
index 313c478f0fd..1bfb50ddca9 100644
--- a/rdf/content/src/nsXULDocument.h
+++ b/rdf/content/src/nsXULDocument.h
@@ -525,6 +525,7 @@ protected:
 
     nsVoidArray mForwardReferences;
     nsForwardReference::Phase mResolutionPhase;
+    PRInt32 mNextContentID;
 
     // The following are pointers into the content model which provide access to
     // the objects triggering either a popup or a tooltip. These are marked as
diff --git a/rdf/content/src/nsXULElement.cpp b/rdf/content/src/nsXULElement.cpp
index 864507347ac..5f82f2aa664 100644
--- a/rdf/content/src/nsXULElement.cpp
+++ b/rdf/content/src/nsXULElement.cpp
@@ -2717,14 +2717,15 @@ nsXULElement::HandleDOMEvent(nsIPresContext* aPresContext,
 NS_IMETHODIMP
 nsXULElement::GetContentID(PRUint32* aID)
 {
-    *aID = 0;
-    return NS_ERROR_NOT_IMPLEMENTED;
+    *aID = mContentId;
+    return NS_OK;
 }
 
 NS_IMETHODIMP
 nsXULElement::SetContentID(PRUint32 aID)
 {
-    return NS_ERROR_NOT_IMPLEMENTED;
+    mContentId = aID;
+    return NS_OK;
 }
 
 NS_IMETHODIMP 
diff --git a/rdf/content/src/nsXULElement.h b/rdf/content/src/nsXULElement.h
index bc229b04f68..5b7e6dc2b39 100644
--- a/rdf/content/src/nsXULElement.h
+++ b/rdf/content/src/nsXULElement.h
@@ -519,6 +519,7 @@ protected:
     nsCOMPtr<nsISupportsArray>          mChildren;           // [OWNER]
     nsCOMPtr<nsIEventListenerManager>   mListenerManager;    // [OWNER]
     void*                               mScriptObject;       // [OWNER]
+    PRInt32                             mContentId;
 
     // The state of our sloth for lazy content model construction via
     // RDF; see nsIXULContent and nsRDFGenericBuilder.