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

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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.

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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.