How can I use GWT together with Visual Studio to create an ASP.NET website? If it is possible.
You can use GWT to generate the client side code writing in Java and use asp.net for the back end.
It's a little trickier as you won't get the serialization across the wire for free that you'd get from using Java on the back end too.
I wouldn't really recommend this approach it's bound to be a hassle to maintain.
I'd recommend using a good javascript toolkit instead, such as jquery and jquery UI.