Even with indenting, keeping track of nested divs can drive you blind. I was thinking of putting the div id in the end div as a property name. Seems to me it should be legal, but will some browser (probably IE) choke on it? Since there isn't really a property I don't list it since that saves typing, and since it's a property name I don't have to type quotes. I imagine this would throw an error on XHTML, but I avoid that anyway.

<div id='container'>
blah blah
<div id='inside'>
more blah
</div inside>
</div container>