关闭页面的时候弹出提示框
<!doctype html>
<html>
<head>
<meta charset="UTF-8">
<title>Leave Page</title>
<script type="text/javascript">
window.onbeforeunload = function()
{
return "Leave this page?";
}
</script>
</head>
<body>
Contents...
</body>
</html>
<!doctype html>
<html> 
