Paschal L has blogged a couple of interesting methods for doing rollovers. I'm adding these to my box of tricks.
Via DataGridGirl: Microsoft has come up with a hotfix for datagrids to make them 508 compliant. The fix addsUseAccessibleHeader, Caption, and CaptionAlign attributes to the datagrid control. The default setting for UseAccessibleHeader is False. If you set it to true the grid will render with TH tags with scope="col" set.
This is GREAT NEWS for those of us who develop .gov or .mil websites!!!
Now the BAD NEWS! You have to call Microsoft in order to get the patch. GRRRRR! This should be a free download.