将下面代码另存成frame.html研究就行了： 
1<html>
2<head>
3<meta content="text/html; charset=utf-8" http-equiv="Content-Type"/>
4<title>无标题文档</title>
5</head>
6<style>
7<!--
8.ptr{color:red;cursor:hand;font-family:webdings}
9\-->
10</style>
11<script>
12function showandshade()
13{
14if(span1.innerText==3)
15{
16span1.innerText=4
17document.all("td1").style.display="none"
18}
19else
20{
21span1.innerText=3
22document.all("td1").style.display=""
23}
24}
25</script>
26<body leftmargin="0" scroll="no" topmargin="0">
27<table border="0" cellpadding="0" cellspacing="0" height="100%" width="100%">
28<tr height="100%">
29<td height="100%" id="td1" style="display:" width="94">
30<iframe frameborder="0" scrolling="no" src="left.htm" width="70"></iframe>
31</td>
32<td bgcolor="#a4b6d7" onclick="showandshade()" style="font-size:7pt;width:5pt;cursor:default;color=:#ffffff" width="71">
33<span class="ptr" id="span1">3</span>
34</td>
35<td width="*">
36<iframe frameborder="0" height="100%" name="main" scrolling="yes" src="right.htm" width="100%">
37</iframe>
38</td>
39</tr>
40</table>
41</body>
42<script>
43if(window.screen.width<'1024'){showandshade()}
44</script>
45</html>