请帮我看下这个CSS该怎么写呀?
<div id= "container ">
<div id= "header ">
</div>
<div id= "pagebody ">
<div id= "left1 "> 左边 </div>
<div id= "mainbody ">
<div id= "flash "> 上边 </div>
<div id= "childbody ">
<div id= "left "> <div id= "left上 "> <div id= "spring "> 左边 </div> <div id= "left2 "> 右边 </div> </div>
<div id= "left下 "> <div id= "summer "> 左 </div> <div id= "autumn "> 中 </div>
<div id= "winter "> 右 </div>
</div>
</div>
<div id= "right "> AD </div>
</div>
</div>
</div>
<div id= "footer "> </div>
</div>

[解决办法]
不难就是复杂点，关键 "left下 "加上clear:both