下拉框架

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<link href="Untitled-下拉.css" rel="stylesheet" type="text/css" />
<style>
*
{
	margin:0px;
	padding:0px;}
</style>
</head>

<body>
<div class="a" id="a">
<div class="a1" >
<div class="a2" id="a2"><div class="a21" ><div class="a22"></div><div class="a32"></div><div class="a42"></div></div></div>
<div class="a3" id="a3"><div class="a31" ></div></div>
<div class="a4" id="a4"><div class="a41" ></div></div>
</div></div>

</body>
</html>

@charset "utf-8";
/* CSS Document */
/*小矿*/
.a
{
	80px;
	height:40px;
	background-color:#090;
	position:absolute;
	border:1px solid black;
	left:80px;
	top:100px;
	}
	#a/*超出部分隐藏*/
	{overflow:hidden;}
#a:hover/*鼠标放在上边显示*/
{
	overflow:visible}

	.a1
{
	80px;
	height:120px;
	border:1px solid black;
	left:0px;
	top:40px;
	position:absolute;}

.a2
{
	80px;
	height:40px;
	background-color:#F00;
	position:absolute;
	border:1px solid black;
	left:0px;
	top:0px;
	}
	#a2
	{overflow:hidden;}
	#a2:hover
	{
		overflow:visible}
		.a21
		{
			80px;
			height:120px;
			position:absolute;
			border:1px solid black;
			left:80px;
			top:0px;
			background-color:#F00;}	
		     .a22
                  {
	                 80px;
	                height:40px;
	            background-color:#F00;
	              position:absolute;
	                 border:1px solid black;
	                 left:0px;
	                 top:0px;
	                           }
	.a32
{
	80px;
	height:40px;
	background-color:#F00;
	position:absolute;
	border:1px solid black;
	left:0px;
	top:40px;
	}
	.a42
{
	80px;
	height:40px;
	background-color:#F00;
	position:absolute;
	border:1px solid black;
	left:0px;
	top:80px;
	}			
	.a3
{
	80px;
	height:40px;
	background-color:#F0F;
	position:absolute;
	border:1px solid black;
	left:0px;
	top:40px;
	}
	#a3
	{overflow:hidden;}
	#a3:hover
	{
		overflow:visible}
		.a31
		{
			80px;
			height:120px;
			position:absolute;
			border:1px solid black;
			left:80px;
			top:0px;
			background-color:#F0F;}
	.a4
{
	80px;
	height:40px;
	background-color:#F69;
	position:absolute;
	border:1px solid black;
	left:0px;
	top:80px;
	}
	#a4
	{overflow:hidden;}
	#a4:hover
	{
	overflow:visible}
	.a41
		{
			80px;
			height:120px;
			border:1px solid black;
			position:absolute;
			left:80px;
			top:0px;
            background-color:#F69;}