Disable Caching on the browsers in asp.net.

Web page must be requested fresh or new each time from the server. 

On Page Load event write below code:- 

Response.Cache.SetNoStore(); Response.AppendHeader("Pragma","no-cache");   Response.Expires = 0;

So whenever the Page_Load event occurs, it will ask a new copy from server, so that we can write code which will check that whether the request is valid or not.