jquery 谷歌浏览器attr取值问题

页面a.aspx

   <title>JUI-框架</title>
    <script src="js/jquery-1.6.2.js" type="text/javascript"></script>
    <link href="css/Style.css" rel="stylesheet" type="text/css" id="skin_css" />
    <script type="text/javascript">
    function initFrame()
    {
        document.frames['left'].initFrame();
    }
    window.onresize = initFrame;
   </script>
</head>
 <frameset border="0" id="main" name="dseg" framespacing="0" rows="62,2*,1" frameborder="no" cols="*">
    <frame name="topFrame" src="top.aspx"  scrolling="no">
    <frameset rows="*" cols="180,7,*" framespacing="0" frameborder="NO" border="0" id="myFrame">
        <frame id="left" name="left" src="left.aspx"  scrolling="no" class="mainLeftFrame">
        <frame name="middle" src="middle.htm" scrolling="no">
        <frame id="right" name="right" src="None.aspx"  scrolling="auto" class="mainRightFrame" style="overflow-x:hidden;">
    </frameset>
 </frameset>
<noframes></noframes>
</html>在top.aspx页面 设置skin_css的属性为
 $(window.parent.frames.main.document).find("#skin_css").attr("href","themes/blue/css/Style.css");

IE内核弹出的属性是正确的值themes/blue/css/Style.css

谷歌浏览器弹出则是undefined

补充：.NET技术 ,  ASP.NET