IE关闭时判断及AJAX注销案例学习

<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) {

try {
var xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
xmlhttp.open("POST", "LogOut.aspx", false);
xmlhttp.send();
//return true;
}
catch (e) {
alert('delete user account error message:' + e.message);
}

//return "你确定要退出系统吗？退出请按'离开此页'";
} else {
//alert("是刷新而非关闭");
}
}

</script>