Hixie is showing how browsers handle tag soup. The way IE does it, is a serious problem for Xopus. Xopus allows pasting of HTML. Unfortunately tools like Outlook paste HTML like this:

<P>text<FONT COLOR=#0000FF><P>text<P>text</FONT>

Xopus then walks the DOM tree. The parent element has 3 <P> elements. The first <P> element has 2 childnodes, a textnode and a <FONT> element. But then when you ask IE's DOM the childnodes of the <FONT> element, it gives the last 2 <P> elements, again. Xopus can validate this, to get proper XHTML, but rule no.1 of the validation routine is to never throw away content. The result: pasting from Outlook sometimes gives you part of the text twice. Those are the bugs you just don't want to fix...