See this

You can disable back button of browser. Use this for same;

<script language="JavaScript">
window.history.forward(1);
</script>

Or

Try adding the following to your page so that the browser will not cache the page:

<META HTTP-EQUIV="Expires" CONTENT="Tue, 01 Jan 1980 1:00:00 GMT">
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">

Just go through following links for more information;

http://www.eggheadcafe.com/community/aspnet/3/10014143/disable-back-button-of-br.aspx

http://www.experts-exchange.com/Web/Web_Languages/JavaScript/Q_20828609.html

http://www.daniweb.com/forums/thread35732.html

http://www.theserverside.com/discussions/thread.tss?thread_id=34644

http://forums.devarticles.com/javascript-development-22/is-there-a-way-to-disable-the-back-button-5408.html

Best luck;
Sujit.