关闭页面询问用户

function close() //关闭页面时询问用户
{
    var n = window.event.screenX - window.screenLeft;
    var b = n > document.documentElement.scrollWidth-20;

    if (b && window.event.clientY < 0 || window.event.altKey)
    {
        window.event.returnValue = "";
    }
}

onbeforeunload="close();"//写在页面body的onbeforeunload事件中