增加一个html页面，定义frameset，如下：
<frameset cols="*,1024,*" frameborder="no" border="0" framespacing="0">
<frame src="about:blank"></frame>
<frameset cols="178,10,*" frameborder="no" border="0" framespacing="0" id="MainFrame">
<frame src="Left.aspx" name="left" scrolling="no" id="left" title="left" />
<frame id="leftbar" scrolling="no" noresize="" name="switchLeftFrame" src="switchLeft.html"/>
<frame src="center.aspx" name="center" id="center" title="center" scrolling="auto" />
</frameset>
<frame src="about:blank"></frame>
</frameset>
<noframes>
</noframes>
switchLeft.html文件：
<html>
<head>
<title>cssrain</title>
<meta charset="gb2312" content="text/html;" http-equiv="Content-Type"/>
<script language="javascript">
function switchSysBar()
{
if (parent.document.getElementById('MainFrame').cols=="178,10,*")
{
document.getElementById('leftbar').style.display="";
parent.document.getElementById('MainFrame').cols="0,10,*";
}
else
{
parent.document.getElementById('MainFrame').cols="178,10,*";
document.getElementById('leftbar').style.display="none"
}
}
function load()
{
if (parent.document.getElementById('MainFrame').cols=="178,10,*")
{
}
}
</script>
</head>
<body marginwidth="0" marginheight="0" bgcolor="#000000" onload="load()" topmargin="0" leftmargin="0">
<center>
<table height="100%" cellspacing="0" cellpadding="0" border="0" width="100%">
<tbody>
<tr>
<td bgcolor="#009fef" width="1">
<img height="1" width="1" src="images/ccc.gif"/>
</td>
<td id="leftbar" bgcolor="#f5f4f4" style="display: none;">
<a onclick="switchSysBar()" href="javascript:void(0);">
<img height="90" border="0" width="9" alt="展开左侧菜单" src="images/pic01.gif"/>
</a>
</td>
<td id="rightbar" bgcolor="#f5f4f4">
<a onclick="switchSysBar()" href="javascript:void(0);">
<img height="90" border="0" width="9" alt="隐藏左侧菜单" src="images/pic02.gif"/>
</a>
</td>
</tr>
</tbody>
</table>
</center>
</body>
</html>
