百分相送。。如何实现在dreamweaverMX软件界面中的框架隐藏效果？

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>Test</title>
<style type="text/css">
<!--
.changes {
font-family: "Webdings";
font-size: 9pt;
color: #FFFFFF;
cursor: hand;
}
-->
</style>
</head>
<script>
function dochange()
{if(left.style.display=="")
   {left.style.display="none";
    right.style.width="100%";
aa.innerHTML="4"
   }
 else
   {aa.innerHTML="3"
    right.style.width="85%";
left.style.display="";
   }   
middle.style.width="1px";
}
</script>
<body leftmargin="0" topmargin="0" marginwidth="0" marginheight="0">
<table height="100%" id=left width="15%" border="0" align="left" cellpadding="0" cellspacing="0">
  <tr>
    <td height="100%" bgcolor="#990099">&nbsp;</td>
  </tr>
</table>
<table  height="100%"  width="85%" id="right" border="0" align="left" cellpadding="0" cellspacing="0">
  <tr> 
    <td height="100%"  id="middle" bgcolor="#0099FF" style="width:1px"><A id="aa" class="changes" onClick="dochange()" >3</A></td>
    <td bgcolor="#000000" id="myiframe"><iframe scrolling="no" src="add.htm" frameborder="0" name="main" width="100%" height="100%"></iframe></td>
  </tr>
</table>
</body>
</html>