Gmail - Back button click on browser

after logging into GMail and clicking the back button on the browser the site开发者_如何学Python doesn't gets back to user login screen? how is it done? Any pointers in java server side programming will be helpful. How to do it without java script.

They probably use HTTP cookies and server side sessions to track the user authentication state. Take a look at this article for more info about using cookies to persist login info.