Here's a informational blog post:
http://rakaz.nl/item/how_well_do_browse ... _selectors
Seems IE7 even is far behind the like of Firefox. If that's true of the final IE7 release... If anything, this demonstrates MS have a long road to travel before catching up with Firefox (which has FF2 on release later today with Javascript 7 and client caching). Does httpOnly cookies stack up FF2's improvements? I think not...
Check the blog entry and linked to browser tests - you can run your own tests, and click orange/red rows for extra details. I tested IE6 and it showed the standard attribute=value test fails if an attribute value is uppercase. Check you html, and make sure all attributes and their values are
lowercase where possible (obviously not for real text though...). Also delete any whitespace between the quotes and a value, which is flagged as another reason for IE6 to fail.