Is it the plan to follow what the specification says or does it need to be changed for the above reason for example?I don't know.Ok.
For what it's worth I will strongly argue that Firefox should return null (assuming the spec says so). I can't say it bothers me that .responseXML.getElementById fails, it isn't hard for the author to address. If authors don't address it because they expect to always get a document, then the above will throw which seems like desired behaviour.
/ Jonas
