ok, so I forgot about rdf content. Now it has range gravity hooks, which do nothing.

rdf/src/nsRDFElement.cpp

@@ -1180,6 +1180,23 @@ nsRDFElement::HandleDOMEvent(nsIPresContext& aPresContext,
 }
 
 
+
+NS_IMETHODIMP 
+nsRDFElement::RangeAdd(nsIDOMRange& aRange) 
+{  
+    // rdf content does not yet support DOM ranges
+    return NS_OK;
+}
+
+
+ 
+NS_IMETHODIMP 
+nsRDFElement::RangeRemove(nsIDOMRange& aRange) 
+{
+    // rdf content does not yet support DOM ranges
+    return NS_OK;
+}                                                                        
+
 ////////////////////////////////////////////////////////////////////////
 // nsIXMLContent
 

rdf/src/nsRDFElement.h

@@ -96,6 +96,8 @@ public:
                               nsIDOMEvent** aDOMEvent,
                               PRUint32 aFlags,
                               nsEventStatus& aEventStatus);
+    NS_IMETHOD RangeAdd(nsIDOMRange& aRange);
+    NS_IMETHOD RangeRemove(nsIDOMRange& aRange); 
 
     // nsIXMLContent (from nsIRDFContent)
     NS_IMETHOD SetNameSpacePrefix(nsIAtom* aNameSpace);