Builtwith.com let's you find out what server technology and tools were used to build a web site. Bookmark this link as it's hard to find later by googling for "what's" etc. which will take you to the what's service where you learn only about the server tech stack installed. Btw, builtwith.com was built with ASP.NET;)
Dirk Dot Net
Creator of useful things. Based in Chiang Mai, Northern Thailand.