设置页面过时时间及重定向 点叉关闭或alt+F4时

<SCRIPT LANGUAGE="JavaScript">
<!--
 window.onbeforeunload = function() { 
   var n = window.event.screenX - window.screenLeft; 
   var b = n > document.documentElement.scrollWidth-20; 
   if(b && window.event.clientY < 0 || window.event.altKey) {//点叉关闭或alt+F4时
    alert("流程未完成");   
   }else{
    //alert("刷新"+location.href+"to ");
   }
  }
//-->
</SCRIPT>