代码简介：
CSS+JavaScript经典版折叠、合拢的多级菜单，这个菜单还是值得研究一下的，一共可展开三层，最里面一级用滚动条来显示菜单内容，整个菜单竖直风格，放到网页的左侧或当作后台管理菜单的模块貌似还不错。
代码内容：
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>JavaScript+CSS折叠、合拢的多级菜单_网页代码站(www.webdm.cn)</title>
<style>
*,body,ul,li,h1,h2{ margin:0; padding:0; list-style:none;}
body{font:12px "宋体"; padding-top:20px;}
#menu { 200px; margin:auto;}
#menu h1 { cursor:pointer; color:#FFF; font-size:12px; padding:5px 0 3px 10px; border:#C60 1px solid; margin-top:1px; background-
color:#F93;}
#menu h2 { cursor:pointer; color:#777; font-size:12px; padding:5px 0 3px 10px; border:#E7E7E7 1px solid; border-top-color:#FFF;
background-color:#F4F4F4;}
#menu ul { padding-left:15px; height:100px;border:#E7E7E7 1px solid; border-top:none;overflow:auto;}
#menu ul li {padding:5px 0 3px 10px;}
.no { display:none;}
</style>
<script language="JavaScript">
<!--//
function ShowMenu(obj,noid){
var block = document.getElementById(noid);
var n = noid.substr(noid.length-1);
if(noid.length==4){
var ul = document.getElementById(noid.substring(0,3)).getElementsByTagName("ul");
var h2 = document.getElementById(noid.substring(0,3)).getElementsByTagName("h2");
for(var i=0; i<h2.length;i++){
h2[i].innerHTML = h2[i].innerHTML.replace("+","-");
h2[i].style.color = "";
}
obj.style.color = "#FF0000";
for(var i=0; i<ul.length; i++){if(i!=n){ul[i].className = "no";}}
}else{
var span = document.getElementById("menu").getElementsByTagName("span");
var h1 = document.getElementById("menu").getElementsByTagName("h1");
for(var i=0; i<h1.length;i++){
h1[i].innerHTML = h1[i].innerHTML.replace("+","-");
h1[i].style.color = "";
}
obj.style.color = "#0000FF";
for(var i=0; i<span.length; i++){if(i!=n){span[i].className = "no";}}
}
if(block.className == "no"){
block.className = "";
obj.innerHTML = obj.innerHTML.replace("-","+");
}else{
block.className = "no";
obj.style.color = "";
}
}
//-->
</script>
</head>
<body>
<div id="menu">
<h1 onClick="javascript:ShowMenu(this,'NO0')"> - 一级菜单A</h1>
<span id="NO0" class="no">
<h2 onClick="javascript:ShowMenu(this,'NO00')"> - 一级菜单A_1</h2>
<ul id="NO00" class="no">
<li>一级菜单A_0</li>
<li>一级菜单A_1</li>
<li>一级菜单A_2</li>
<li>一级菜单A_3</li>
<li>一级菜单A_4</li>
<li>一级菜单A_5</li>
</ul>
<h2 onClick="javascript:ShowMenu(this,'NO01')"> - 一级菜单A_2</h2>
<ul id="NO01" class="no">
<li>一级菜单A_0</li>
<li>一级菜单A_1</li>
<li>一级菜单A_2</li>
<li>一级菜单A_3</li>
<li>一级菜单A_4</li>
</ul>
<h2 onClick="javascript:ShowMenu(this,'NO02')"> - 一级菜单A_3</h2>
<ul id="NO02" class="no">
<li>一级菜单A_0</li>
<li>一级菜单A_1</li>
<li>一级菜单A_2</li>
<li>一级菜单A_3</li>
<li>一级菜单A_4</li>
<li>一级菜单A_5</li>
<li>一级菜单A_6</li>
</ul>
<h2 onClick="javascript:ShowMenu(this,'NO03')"> - 一级菜单A_4</h2>
<ul id="NO03" class="no">
<li>一级菜单A_0</li>
<li>一级菜单A_1</li>
<li>一级菜单A_2</li>
<li>一级菜单A_3</li>
<li>一级菜单A_4</li>
<li>一级菜单A_5</li>
<li>一级菜单A_6</li>
<li>一级菜单A_7</li>
</ul>
</span>
<h1 onClick="javascript:ShowMenu(this,'NO1')"> - 二级菜单B</h1>
<span id="NO1" class="no">
<h2 onClick="javascript:ShowMenu(this,'NO10')"> - 二级菜单B_1</h2>
<ul id="NO10" class="no">
<li>二级菜单B_0</li>
<li>二级菜单B_1</li>
<li>二级菜单B_2</li>
<li>二级菜单B_3</li>
<li>二级菜单B_4</li>
<li>二级菜单B_5</li>
<li>二级菜单B_6</li>
<li>二级菜单B_7</li>
</ul>
<h2 onClick="javascript:ShowMenu(this,'NO11')"> - 二级菜单B_2</h2>
<ul id="NO11" class="no">
<li>二级菜单B_0</li>
<li>二级菜单B_1</li>
<li>二级菜单B_2</li>
<li>二级菜单B_3</li>
<li>二级菜单B_4</li>
<li>二级菜单B_5</li>
<li>二级菜单B_6</li>
<li>二级菜单B_7</li>
</ul>
</span>
<h1 onClick="javascript:ShowMenu(this,'NO2')"> - 三级菜单C</h1>
<span id="NO2" class="no">
<h2 onClick="javascript:ShowMenu(this,'NO20')"> - 三级菜单C_1</h2>
<ul id="NO20" class="no">
<li>三级菜单C_0</li>
<li>三级菜单C_1</li>
<li>三级菜单C_2</li>
<li>三级菜单C_3</li>
<li>三级菜单C_4</li>
<li>三级菜单C_5</li>
<li>三级菜单C_6</li>
<li>三级菜单C_7</li>
<li>三级菜单C_8</li>
<li>三级菜单C_9</li>
</ul>
<h2 onClick="javascript:ShowMenu(this,'NO21')"> - 三级菜单C_2</h2>
<ul id="NO21" class="no">
<li>三级菜单C_0</li>
<li>三级菜单C_1</li>
<li>三级菜单C_2</li>
<li>三级菜单C_3</li>
<li>三级菜单C_4</li>
</ul>
</span>
<h1 onClick="javascript:ShowMenu(this,'NO3')"> - 四级菜单D</h1>
<span id="NO3" class="no">
<h2 onClick="javascript:ShowMenu(this,'NO30')"> - 四级菜单D_1</h2>
<ul id="NO30" class="no">
<li>四级菜单D_0</li>
<li>四级菜单D_1</li>
<li>四级菜单D_2</li>
<li>四级菜单D_3</li>
</ul>
<h2 onClick="javascript:ShowMenu(this,'NO31')"> - 四级菜单D_2</h2>
<ul id="NO31" class="no">
<li>四级菜单D_0</li>
<li>四级菜单D_1</li>
<li>四级菜单D_2</li>
<li>四级菜单D_3</li>
<li>四级菜单D_4</li>
<li>四级菜单D_5</li>
</ul>
</span>
</div>
</body>
</html>
<br>
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代码来自：http://www.webdm.cn/webcode/d489b1a1-785f-44e4-a5c1-29df6f5f528c.html