HTTP protocol, used for communication between web browser and web server, can't identify certain visitor between two requests. When web page is downloaded to client, connection is closed and server deletes all visitor's data. We say that HTTP protocol is stateless. To solve this problem and to maintain visitor's state between requests, ASP.NET introduces Session object. This tutorial explains ASP.NET Session, how it works, different session modes, state compression, cookieless session and more.