1. 程序代码如下：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>CSS+JS实现兼容性很好的无限级下拉菜单</title>
<style type="text/css">
*{ margin:0; padding:0; border:0;}
body{font:12px/130% verdana,geneva,arial,helvetica,sans-serif,宋体;}li{list-style:none;}
.clearfix:after{content:" ";display:block;height:0;clear:both;visibility:hidden;}.clearfix{display:inline-block;}
a:link{ color:#000; text-decoration:none; }
a:visited{ color:#000; text-decoration:none; }
a:hover{ color:#000; text-decoration:none; }
.menu{ width:778px; height:26px; background:#fff; margin:0 auto;}
.menusel{ float:left;width:100px; position:relative; height:25px; background:#ddd; line-height: 25px; margin-left: 1px; *margin-left: 0px;_margin-left: -1px;}
.menusel h2{ font-size:12px; }
.menusel a{ display: block;text-align:center; width:100px;border:1px solid #a4a4a4; height:25px; border-bottom:1px solid #a4a4a4; position:relative; z-index:2;}
.menusel a:hover{ border:1px solid #a4a4a4; border-bottom:1px dashed #eeeeee; position:relative; z-index:2; height:25px;}
.ahover a{border-bottom:1px dashed #eeeeee; background:#eeeeee; }
.position{ position:absolute; z-index:1;}
.menusel ul{width:125px; background:#eee; border:1px solid #a4a4a4; margin-top: -1px; position:relative; z-index:1; display:none;}
.menusel .block{ display:block;}
.typeul li{border-bottom:1px dashed #a4a4a4;width:125px; position:relative; float:left; }
.typeul li a{ border:none;width:125px; }
.typeul li a:hover{ border:none; background:#ddd;}
.typeul{ margin-left:0; }
.typeul ul{left:125px; top:0; position:absolute;}
.fli{ margin-left: -1px; border-left:#eeeeee solid 1px;}
.menusel .lli{ border:none; }
</style>
<script type="text/javascript">document.execCommand("BackgroundImageCache", false, true);</script><!-- IE6背景图片闪烁问题 -->
</head>
<body>
<div class="menu">
<div id="menu1" class="menusel">
<h2><a href="/">菜单1</a></h2>
<div class="position">
<ul class="clearfix typeul">
<li><a href="//www.VeVB.COm">菜单选项1-2</a></li>
<li>
<a href="#">菜单选项1-2</a>
<ul>
<li class="fli"><a href="#">菜单选项1-2-1</a></li>
<li class="lli"><a href="#">菜单选项1-2-2</a></li>
</ul>
</li>
<li><a href="//www.VeVB.COm">菜单选项1-2</a></li>
<li class="lli"><a href="#">菜单选项1-2</a></li>
</ul>
</div><!-- position -->
</div><!-- menusel -->
<div id="menu2" class="menusel">
<h2><a href="#">菜单2</a></h2>
<div class="position">
<ul class="clearfix typeul">
<li><a href="#">菜单选项2-2</a></li>
<li><a href="#">菜单选项2-2</a>
<ul>
<li class="fli"><a href="#">菜单选项2-2-1</a></li>
<li class="lli"><a href="#">菜单选项2-2-2</a>
<ul>
<li class="fli"><a href="#">菜单选项2-2-1</a></li>
<li class="lli"><a href="#">菜单选项2-2-2</a>
</li>
</ul>
</li>
</ul>
</li>
<li><a href="#">菜单选项2-2</a></li>
<li class="lli"><a href="#">菜单选项2-2</a></li>
</ul>
</div><!-- position -->
</div><!-- menusel -->
<div id="menu3" class="menusel">
<h2><a href="#">菜单3</a></h2>
<div class="position">
<ul class="clearfix typeul">
<li><a href="#">菜单选项3-2</a></li>
<li><a href="#">菜单选项3-2</a>
<ul>
<li class="fli"><a href="#">菜单选项3-2-1</a></li>
<li class="lli"><a href="#">菜单选项3-2-2</a>
<ul>
<li class="fli"><a href="#">菜单选项3-2-1</a></li>
<li class="lli"><a href="#">菜单选项3-2-2</a>
<ul>
<li class="fli"><a href="#">菜单选项3-2-1</a></li>
<li class="lli"><a href="#">菜单选项3-2-2</a></li>
</ul>
</li>
</ul>
</li>
</ul>
</li>
<li><a href="#">菜单选项3-2</a></li>
<li class="lli"><a href="#">菜单选项3-2</a></li>
</ul>
</div><!-- position -->
</div><!-- menusel -->
</div><!-- menu -->
<script type="text/javascript">
for(var x = 1; x < 4; x++)
{
var menuid = document.getElementById("menu"+x);
menuid.num = x;
type();
}
function type()
{
var menuh2 = menuid.getElementsByTagName("h2");
var menuul = menuid.getElementsByTagName("ul");
var menuli = menuul[0].getElementsByTagName("li");
menuh2[0].onmouseover = show;
menuh2[0].onmouseout = unshow;
menuul[0].onmouseover = show;
menuul[0].onmouseout = unshow;
function show()
{
menuul[0].className = "clearfix typeul block"
}
function unshow()
{
menuul[0].className = "typeul"
}
for(var i = 0; i < menuli.length; i++)
{
menuli[i].num = i;
var liul = menuli[i].getElementsByTagName("ul")[0];
if(liul)
{
typeshow()
}
}
function typeshow()
{
menuli[i].onmouseover = showul;
menuli[i].onmouseout = unshowul;
}
function showul()
{
menuli[this.num].getElementsByTagName("ul")[0].className = "block";
}
function unshowul()
{
menuli[this.num].getElementsByTagName("ul")[0].className = "";
}
}
</script>
</body>
</html>
2. 程序效果
