.
clientx clientY beforeunload. ...
<script type="text/javascript">
var myclose = false;
function ConfirmClose()
{
if (event.clientY < 0)
{
event.returnValue = 'Any message you want';
setTimeout('myclose=false',100);
myclose=true;
}
}
function HandleOnClose()
{
if (myclose==true) alert("Window is closed");
}
</script> onbeforeunload="ConfirmClose()" onunload="HandleOnClose()"