CSS灰色下拉菜单，支持二级的导航菜单，如果不喜欢灰色的话，颜色你自己调整下，完善后效果是相当不错的。
<!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>
<title>灰色下拉导航菜单 by www.codefans.net</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<style type="text/css">
body { font-family:Arial, Sans-Serif; font-size:13px; margin:0px;
background: transparent url(http://www.codefans.net/jscss/demoimg/201107/page_bkg.png) repeat scroll top center;}
h1 {margin:0px; padding:20px 0 0 20px;}
p {padding:20px; color:#dcdcdc;}
p a {color:#9BD800;}
p a:hover {color:#B6FF00;}
#header { height:120px; position:relative;
background: transparent url(http://www.codefans.net/jscss/demoimg/201107/header_bkg.png) repeat-x scroll top center;}
#nav { margin:0px; padding:0px; position:absolute; top: 70px; display:block;}
#nav > li { list-style-type:none; float:left; display:block; margin:0px 10px;
position:relative; padding:10px; width:100px;}
#nav > li:hover ul { display:block; }
#nav > li:hover { background-color:#808080; -moz-border-radius:10px; -webkit-border-radius:10px; }
#nav li ul { margin:0px; padding:0px; display:none;}
#nav li ul li { list-style-type:none; margin:10px 0 0 0;}
#nav li ul li a { display:block; padding:5px 10px; color:#A2E200; text-decoration:none;}
#nav li ul li:hover a { background-color:#606060; -moz-border-radius:5px; -webkit-border-radius:5px;}
#nav li span { cursor:pointer; margin:0px 10px; font-weight:bold; }
</style>
</head>
<body>
<div id="header">
<h1>灰色下拉导航菜单</h1>
<ul id="nav">
<li><span>Menu 1</span>
<ul>
<li><a href="/">Menu item 1</a></li>
<li><a href="/">Menu item 2</a></li>
<li><a href="/">Menu item 3</a></li>
</ul>
</li>
<li><span>Menu 2</span>
<ul>
<li><a href="/">Menu item 1</a></li>
<li><a href="/">Menu item 2</a></li>
<li><a href="/">Menu item 3</a></li>
</ul>
</li>
<li><span>Menu 3</span>
<ul>
<li><a href="/">Menu item 1</a></li>
<li><a href="/">Menu item 2</a></li>
<li><a href="/">Menu item 3</a></li>
</ul>
</li>
</ul>
</div>
</body>
</html>
