div+css 基本布局：
<div id="mm">
<div id="aa"></div>
<div id="bb"></div>
</div>
<script type="text/javascript">
<!--
window.onload=window.onresize=function aa()
{
if(document.getElementById("bb").clientHeight<document.getElementById("aa").clientHeight)
{
document.getElementById("bb").style.height=document.getElementById("aa").offsetHeight+"px";
}
else
{
document.getElementById("aa").style.height=document.getElementById("bb").offsetHeight+"px";
}
}
-->
</script>