The new version of IE8 will have three modes of operation. Quirks, standard, and super-standard. These roughly correspond to compatibility with IE4/5/6; IE7 and W3C standards. They are making super-standards the default.
The good news (for some) is that you can add a meta-teg to tell IE8 to revert to IE7 standards. So it is fairly simple to get by if you are having problems with IE8. This gives you a let-out if you had to go non-standard to make your design work with IE7.
Bob Browning's blog 
Leave a comment