frame显示问题。

---------------all.htm--------------
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>无标题文档</title>
</head><frameset rows="80,*" frameborder="no" border="0" framespacing="0">
  <frame src="a.htm" name="topFrame" scrolling="No" noresize="noresize" id="topFrame" title="topFrame" />
  <frame src="b.htm"" name="mainFrame" id="mainFrame" title="mainFrame" />
</frameset>
<noframes><body>
</body>
</noframes></html>------------a.htm---------------------
...
<a href="javascript:parent.window.frames['mainFrame'].location='b.htm'">
test
</a>
....
---------------b.htm-------------
随便写