I was checking to know what the .NET framework is exactly. I understand that ASP.NET is just built over the .NET and that it uses all the web-technologies-services of .NET and all the web site design company also use this .Net. So to do this I believe that they must use the same underlying Class Library as of the .NET to build ASP.NET technology. And also for us as users to develop ASP.NET applications we need to use these classes.