原地址：http://www.cnblogs.com/lancee/archive/2011/07/07/2100258.html
<!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>三级dropdown弹出菜单</title>
<style type="text/css">/* common styling */
.menu {
font-family: arial, sans-serif;
750px;
position: relative;
font-size: 11px;
margin: 50px 0;
}
.menu ul li a, .menu ul li a:visited {
display: block;
text-decoration: none;
104px;
height: 20px;
text-align: center;
color: #fff;
border: 1px solid #fff;
background: #710069;
line-height: 20px;
font-size: 11px;
overflow: hidden;
}
.menu ul {
padding: 0;
margin: 0;
list-style-type: none;
}
.menu ul li {
float: left;
margin-right: 1px;
position: relative;
}
.menu ul li ul {
display: none;
}
/* specific to non IE browsers */
.menu ul li:hover a {
color: #fff;
background: #36f;
}
.menu ul li:hover ul {
display: block;
position: absolute;
top: 21px;
left: 0;
105px;
}
.menu ul li:hover ul li a.hide {
background: #6a3;
color: #fff;
}
.menu ul li:hover ul li:hover a.hide {
background: #6fc;
color: #000;
}
.menu ul li:hover ul li ul {
display: none;
}
.menu ul li:hover ul li a {
display: block;
background: #ddd;
color: #000;
}
.menu ul li:hover ul li a:hover {
background: #6fc;
color: #000;
}
.menu ul li:hover ul li:hover ul {
display: block;
position: absolute;
left: 105px;
top: 0;
}
.menu ul li:hover ul li:hover ul.left {
left: -105px;
}
</style>
</head>
<body>
<div class="menu">
<ul>
<li><a class="hide" href="../menu/index.html">DEMOS</a>
<ul>
<li><a href="../menu/nodots.html" title="Removing active/focus borders">active focus</a></li>
<li><a class="hide" href="../menu/hover_click.html" title="Hover/click with no active/focus borders">HOVER/CLICK></a>
<ul>
<li><a href="../menu/form.html" title="Styling forms">styled form</a></li>
<li><a href="../menu/nodots.html" title="Removing active/focus borders">active focus</a></li>
<li><a href="../menu/hover_click.html" title="Hover/click with no active/focus borders">hover/click</a>
</li>
</ul>
</li>
</ul>
</li>
<li><a class="hide" href="../opacity/index.html">OPACITY</a>
<ul>
<li><a href="../opacity/colours.html" title="colour wheel">opaque colours</a></li>
<li><a class="hide" href="../menu/hover_click.html" title="Hover/click with no active/focus borders">HOVER/CLICK</a>
<ul class="left">
<li><a href="../menu/form.html" title="Styling forms">styled form</a></li>
</li>
</ul>
</li>
</ul>
</li>
</ul>
</div>
</body>
</html>