离开页面前显示确认提示对话框(IE,firefox 都兼容)

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html>
<head>
   <title>Untitled</title>
   <script type="text/javascript">
   window.onbeforeunload = function()
   {
       return ('您确定要离开此页面吗?');
   }
   </script>
</head>
<body>
<a href="http://www.baidu.com">百度</a>
</body>
</html>