Detect browser back button to logout

<script type="text/javascript" language="javascript">
window.history.forward(1);
document.attachEvent("onkeydown", my_onkeydown_handler);
function my_onkeydown_handler()
{
switch (event.keyCode)
{
case 116 : // F5;
event.returnValue = false;
event.keyCode = 0;
window.status = "We have disabled F5";
break;
}
}
</script>

Session.Clear();
Session.Abandon();