写一个table
<table width='100%' height='100%'>
<tr>
<td width='80%' height='80%'>
<iframe name='a' width='100%' height='100%'></iframe>
</td>
<td width='20%' height='100%' rowspan=2>
<iframe name='c' width='100%' height='100%'></iframe>
</td>
<td width='80%' height='20%'>
<iframe name='b' width='100%' height='100%'></iframe>
</td></table>
<table width='100%' height='100%'>
<tr>
<td width='80%' height='80%'>
<iframe name='a' width='100%' height='100%'></iframe>
</td>
<td width='20%' height='100%' rowspan=2>
<iframe name='c' width='100%' height='100%'></iframe>
</td>
<td width='80%' height='20%'>
<iframe name='b' width='100%' height='100%'></iframe>
</td></table>
<table width="100%" height="100%" border="0" cellpadding="0" cellspacing="0">
<tr>
<td width="80%" height="80%"><iframe width="100%" height="100%" src="a.htm" frameborder="0"></iframe></td>
<td width="20%" height="100%" rowspan="2"><iframe width="100%" height="100%" src="a.htm" frameborder="0"></iframe></td>
</tr>
<tr>
<td width="80%" height="20%"><iframe width="100%" height="100%" src="a.htm" frameborder="0"></iframe></td>
</tr>
</table>
</body>
<tr>
<td width='80%' height='80%'>
<iframe name='a' width='100%' height='100%'></iframe>
</td>
<td width='20%' height='100%' rowspan=2>
<iframe name='c' width='100%' height='100%'></iframe>
</td>
</tr>
<tr>
<td width='80%' height='20%'>
<iframe name='b' width='100%' height='100%'></iframe>
</td>
</tr></table>