实例：CSS二级菜单（横向）兼容IE6、IE7、FF浏览器
源码：
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>http://hi.baidu.com/cyaning</title>
<style type="text/css">
<!--
*{margin:0;padding:0;border:0;}
body {font-family: 宋体;font-size:12px;}
#nav {line-height: 24px;list-style-type: none;background:#666;}
#nav a {display: block;width: 80px;text-align:center;}
#nav a:link {color:#666;text-decoration:none;}
#nav a:visited {color:#666;text-decoration:none;}
#nav a:hover {color:#FFF;text-decoration:none;}
#nav li {float: left;width: 80px;background:#ddd;}
#nav li a:hover{background:#999;}
#nav li ul {line-height: 27px;list-style-type: none;text-align:left;left: -999em;width: 980px;position: absolute;float:left;}
#nav li ul li{float: left;width: 80px;background: #F6F6F6;}
#nav li ul a{display: block;width: 80px;text-align:center;}
#nav li ul a:link {color:#666;text-decoration:none;}
#nav li ul a:visited {color:#666;text-decoration:none;}
#nav li ul a:hover {color:#F3F3F3;text-decoration:none;font-weight:normal;background:#C00;}
#nav li:hover ul {left: 0;}
#nav li.sfhover ul {left: 0;}
-->
</style>
<script type=text/javascript>
function menuFix()
{var sfEls = document.getElementById("nav").getElementsByTagName("li");for (var i=0;i<sfEls.length;i++)
{sfEls[i].onmouseover=function() {this.className+=(this.className.length>0? " ": "") + "sfhover";}
sfEls[i].onMouseDown=function() {this.className+=(this.className.length>0? " ": "") + "sfhover";}
sfEls[i].onMouseUp=function() {this.className+=(this.className.length>0? " ": "") + "sfhover";}
sfEls[i].onmouseout=function() {this.className=this.className.replace(new RegExp("( ?|^)sfhover\\b"), "");}
}
}
window.onload=menuFix;
</script>
</head>
<body>
<ul id="nav">
<li><a href="#">产品介绍</a>
<ul>
<li><a href="#">产品一</a></li>
<li><a href="#">产品一</a></li>
<li><a href="#">产品一</a></li>
<li><a href="#">产品一</a></li>
<li><a href="#">产品一</a></li>
<li><a href="#">产品一</a></li>
</ul>
</li>
<li><a href="#">服务介绍</a>
<ul>
<li><a href="#">服务二</a></li>
<li><a href="#">服务二</a></li>
<li><a href="#">服务二</a></li>
<li><a href="#">服务二服</a></li>
<li><a href="#">服务二服</a></li>
<li><a href="#">服务二</a></li>
</ul>
</li>
<li><a href="#">成功案例</a>
<ul>
<li><a href="#">案例三</a></li>
<li><a href="#">案例</a></li>
<li><a href="#">案例三案</a></li>
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</ul>
</li>
<li><a href="#">关于我们</a>
<ul>
<li><a href="#">我们四</a></li>
<li><a href="#">我们四</a></li>
<li><a href="#">我们四</a></li>
<li><a href="#">我们四111</a></li>
</ul>
</li>
<li><a href="#">在线演示</a>
<ul>
<li><a href="#">演示</a></li>
<li><a href="#">演示</a></li>
<li><a href="#">演示</a></li>
<li><a href="#">演示演示</a></li>
<li><a href="#">演示演示</a></li>
<li><a href="#">演示演示</a></li>
<li><a href="#">演示演示</a></li>
<li><a href="#">演示演示</a></li>
</ul>
</li>
<li><a href="#">联系我们</a>
<ul>
<li><a href="#">联系联系</a></li>
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</ul>
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</ul>
</body>
</html>
