For example, I visit http://www.codeproject.com on a regular basis. I get a lot of great code from them. But, their forum dropdown has a bug in IE 6.0 SP1.
As you can see, the dropdown for the number of posts to show is overwriting the dropdown to select the forum. As a result, you can't even tell which forum that is supposed to be. (It's supposed to be SQL/ADO/ADO.NET.)
Until simple things like this can be done easily and relatively bug-free, we'll be sticking with a simple website.