prevent back button code example
Example: disable back button in browser
<script type="text/javascript"> function preventBack() {window.history.forward();} setTimeout("preventBack()", 0); window.onunload = function () {null};</script>
<script type="text/javascript"> function preventBack() {window.history.forward();} setTimeout("preventBack()", 0); window.onunload = function () {null};</script>