How to start Ajax in asp.net 3.5

In my First Ajax article or Ajax tutorial i have explained generic Ajax basics. In this ajax article or ajax tutorial i will explain "How to learn Ajax in Asp.net 3.5". That means all about asp.net 3.5. In Visual Studio (VS) 2005 ajax required seperate installation but in .Net framework 3.5 you do not need to install anything for ajax. If you are using an Asp.Net version prior to Asp.Net 3.5,