ASP.NET 2.0 applications on IIS 7.0 are hosted using the ASP.NET Integrated mode by default. This new mode enables a myriad of exciting scenarios including using super-valuable ASP.NET features like Forms Authentication for your entire Web site, and developing new ASP.NET modules to do things like URL rewriting, authorization, logging, and more at the IIS level.
As you know, with great power comes great responsibility. Similarly, with making ASP.NET applications more powerful in IIS 7.0 comes the responsibility of making sure that existing ASP.NET applications continue to work. This has been a major challenge for us as we re-architected the entire core engine of ASP.NET, and in the end we were highly successful in meeting it.
This post lists the changes in behavior that you may encounter when deploying your ASP.NET applications on IIS 7.0 on Windows Vista SP1 and Windows Server 2008. Read the detailed list of breaking changes at http://mvolo.com/blogs/serverside/archive/2007/12/08/IIS-7.0-Breaking-Changes-ASP.NET-2.0-applications-Integrated-mode.aspx.