Internet Explorer 7: Expect Compatibility Problems
The beta version of IE7 has been available to developers for a while now, and Microsoft has been begging, pleading and cajoling them to test their web apps with it. Unfortunately, the response from beta testers has been less then positive up to now. If you ever feel like embarking in the IE7 Beta testing experience, prepare yourself for some major heartburns.
"unless you're using pretty much pure HTML on static pages, your application is going to break in some way."