Jamie asks about what is aspnet.config.

Alan has a detailed discussion on binding policies.

http://blogs.gotdotnet.com/alanshi/commentview.aspx/d4edb084-c625-4b6e-8e5c-7c2580cfcee9

And aspnet.config is what Alan described as Host Policy.

I don't really see why you need host policy. In fact, I successfully convinced Asp.Net team to remove this policy in Whidbey. If you have a Whidbey beta1 redist install, you will see aspnet.config is gone.