How can I stop user from navigating to the previous page

I am developing a simple email portal as my college assignment and I refer gmail for various features.Now when we sign into a gmail account and then if we hit the back button of the browser we somehow still remain on the inbox page.In 开发者_运维问答my case after login if I press back button I comeback to the login page.Please suggest how can I achieve this.Also I am a newbie to ASP.NET so keep it detailed

Very simple. When loading the login page, check the user's current session state, and if they're already logged in, redirect them to their inbox.

The trick is to use javascript's "history.replace(...)" function:

http://www.hunlock.com/blogs/Mastering_The_Back_Button_With_Javascript

In essence, you remove previous history entries.