According to a press release from earlier, eWeek has learned that ASP.NET 2.0 breaks existing 1.1 applications. I’ve done my part to test my apps in 2.0 and they all seem to work just fine. Some of the namespaces and classes will eventually go away because of enhanced functionality. So, when building your applications, you should take note of any warnings listed. You can find out more about compatibility at http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnnetdep/html/netfxcompat.asp.