左边iframe放树目录，右边的iframe放index页。拖鼠标同时控制2个iframe的宽高。
期待有人能改进。
操作方法：鼠标指到2个iframe中间，可以水平拖，纵向拖(控制高度)
缺点：CSDN页面放开鼠标后才改大小，不占CPU资源。 这个是实时改大小，所以速度太慢，希望有人来改改。我是不想弄了，反正又没用什么特别的技术。
提示：拖动的秘密就在filter:alpha(opacity=0)这一句
<html>
<script language="javascript">
var mouseX = 0;
var mouseY = 0;
var w=5;
function divonmousemove(){
obj1=document.getElementById("a");
obj2=document.getElementById("b");
obj12=document.getElementById("ab");
if (mouseX!==event.x && mouseY!==event.y)obj12.style.cursor='se-resize';
else if (mouseX!==event.x)obj12.style.cursor='e-resize';
else if (mouseY!==event.y)obj12.style.cursor='s-resize';
else obj12.style.cursor='';
if (event.button==1){
obj1.style.width=parseInt(obj1.offsetWidth)+(event.x - mouseX);
mouseX=event.x;
obj1.style.height=parseInt(obj1.offsetHeight)+(event.y - mouseY);
mouseY= event.y;
obj12.style.width=108;
obj12.style.left=obj1.offsetWidth-obj12.offsetWidth/2;
obj12.style.height=obj1.clientHeight;
obj2.style.height=obj1.clientHeight;
obj2.style.left=obj1.clientWidth+w;
obj2.style.width=screen.width-obj1.offsetWidth-w;
}}
function divonmousedown(){
mouseX = event.x;
mouseY = event.y;
}
function divonmouseup(){
obj12.style.left=obj1.offsetWidth;
obj12.style.width=w;
mouseX = 0;
mouseY = 0;}
</script>
<body style='margin:0'>
<iframe zindex=1 id="a" src="http://community.csdn.net/Tree/tree.htm" style="width:200;height:610;position:absolute;z-index:9 "></iframe>
<div zindex=0 id='ab' onmousemove='divonmousemove();' onmouseleave='document.getElementById("ab").style.cursor='';'
>
< table style="width:100%;height:100%;" border=0 cellspacing=0 cellpadding=0px >
< tr>
< td style="width:150px;" >
< iframe zindex=1 id="a" src="http://community.csdn.net/Tree/tree.htm" style="width:100%;height:100%;z-index:9 "></iframe>
< /td>
< td style="width:3px;cursor:e-resize;background-color:#cccccc;" align="center" valign="middle"
onmousedown="Resize_mousedown(event,this);" onmouseup="Resize_mouseup(event,this);" onmousemove="Resize_mousemove(event,this);">
<font style="size:3px;background-color:#eeeeee;cursor:pointer;" onmousedown="Resize_setDefault(event,this);"><</font>
< /td>
< td>
< iframe zindex=1 id="b" name="ContentFrame" src="http://community.csdn.net/index.htm" style="width:100%;height:100%;z-index:10"></iframe>
< /td>
< /tr>
< /table>
< /body>