.NET 4 includes a new version of the CLR, and a new .NET 4 specific machine.config file (which is installed side-by-side with the one used by .NET 2, 3 and 3.5). The new .NET 4 machine.config file now automatically registers all of the ASP.NET tag sections, handlers and modules that we’ve added over the years, including the functionality for ASP.NET AJAX, ASP.NET Dynamic Data, ASP.NET Routing, ASP.NET Chart Control What this means is that when you create a new “Empty ASP.NET application” project in VS 2010, you’ll find that the new default application-level web.config file is now clean and simple.