You cannot prevent the browser from keeping track of visited pages.
You can trap for the "backspace" key and ignore those requests, but without a lot of work there is no way to prevent the user from navigating backwards (or forwards). And even if you could, the expectation is: It's a browser, so it should BEHAVE like one.
Both IE and FF have a "private browsing" mode where no history is retained, but this DOES NOT prevent the creation of page history, nor disable navigation.,
