Mozilla summary

I have done a quick survey of the Mozilla test results.  Here is a rough breakdown:

About 16 tests fail since document.doctype apparently returns null
About 8 tests fail since default attributes from the DTD are not incorporated
About 8 tests fail since document.createEntityReference apparently returns null
Invalid character, in use and wrong document exceptions aren't raised (probably another 10 cases)
The negative count tests (3) crash Mozilla

About 5 cases fail due to returning "" when the spec specifies null, particularly for Node.value.  As mentioned before this is consistent with null not being in the value set of String in JavaScript.  Eventually we will need some resolution from the WG on this issue.

And then a hodge podge of about 10 cases.