Question

I’ve noticed an awkward occurence in Firefox/Firebug:

<dl>
    <dt><h3>test</h3></dt>
    <dd>stuff</dd>
</dl>

renders as this

<dl>
    <dt></dt>
    <h3>test</h3>
    <dd>stuff</dd>
</dl>

I’ve never seen this happen before. Can anyone explain why?

Answer 1

Probably because it’s invalid XHTML and this is how the Firefox’s error recovery works:

Line 14, Column 12: document type does not allow element “h3” here; missing one of “object”, “ins”, “del”, “map”, “button” start-tag

http://validator.w3.org

FWIW, I tested Chrome, IE and Opera and none of them exhibited the same behavior. This is a solid argument for why you should write valid markup and not rely on the parser’s error recovery – browsers handle errors in their own way.