设立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>