Untitled

jQuery .unload() doesn't show anything
<html>
<head>
    <title>D</title>
    <script type="text/javascript" src="jQuery.js">
    <script type="text/javascript">
    $(window).unload( function () { alert("Bye now!"); } );
    </script>
</head>

<body>
     <span>Hello world</span>
</body>
</html>