About Global.asax file and web.config file

You will need to create a Session variable

Session["UserId"] and check if this variable is null in all pages if yes redirect to login page

After successful login set the UserId of the user in session variable

Ok Sir,

But in web.config file can i do something

Web.Config you can do only for ASP.Net Membership logins. For others you cannot.

What you can do create a Base Class and inherit it in your all pages that require login

In that base class you can do your session checking

http://www.dreamincode.net/forums/topic/45300-base-page-for-detecting-session-timeout-in-aspnetc%23/