将下面代码另存成frame.html研究就行了：
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>无标题文档</title>
</head>
<style>
<!--
.ptr{color:red;cursor:hand;font-family:webdings}
-->
</style>
<script>
function showandshade()
{
if(span1.innerText==3)
{
span1.innerText=4
document.all("td1").style.display="none"
}
else
{
span1.innerText=3
document.all("td1").style.display=""
}
}
</script>
<body leftMargin="0" topMargin="0" scroll=no>
<table width="100%" height="100%" border=0 cellSpacing="0" cellPadding="0">
<tr height="100%">
<td id="td1" width="94" height="100%" style="display:">
<iframe src=left.htm frameborder=0 scrolling=no width="70"></iframe>
</td>
<td width="71" bgColor=#a4b6d7 style="font-size:7pt;width:5pt;cursor:default;color=:#ffffff" onclick="showandshade()">
<span id="span1" class="ptr">3</span>
</td>
<td width="*">
<iframe name="main" src=right.htm frameborder=0 scrolling=yes height="100%" width="100%">
</iframe>
</td>
</tr>
</table>
</body>
<SCRIPT>
if(window.screen.width<'1024'){showandshade()}
</SCRIPT>
</html>