检测关闭浏览器和屏蔽F5

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title></title>
</head>
<body>
    检测浏览器关闭，同时屏蔽F5
    listen browser colse event and disable F5,
</body>
</html>
<script type="text/javascript">
<!--  
    window.onbeforeunload = onbeforeunload_handler;
    window.onunload       = onunload_handler;
    document.onkeydown    = disableF5;
    function onbeforeunload_handler(){
    if(1==1){
    var warning="Close this window?";        
       return warning;
    }
       
    }
    function onunload_handler(){
    
     
    }
    function disableF5(e)
{

    if (!e)
        {
          var e = window.event;
        }
    var keycode = e.keyCode;
    if (e.which)
        keycode = e.which;

    var src = e.srcElement;
    if (e.target)
        {
        src = e.target;   
        }        
    // 116 = F5
if (116== keycode)
    {
        // Firefox and other non IE browsers
if (e.preventDefault)
        {
            e.preventDefault();
            e.stopPropagation();
        }
        // Internet Explorer
elseif (e.keyCode)
        {
            e.keyCode =0;
            e.returnValue =false;
            e.cancelBubble =true;
        }

        returnfalse;
    }
}

-->
</script>
IE6 不行 :(