HTML drop-down menu code

<ul id="nav"> 
<li><a href="http://www.php.cn/">下拉</a> 
    <ul> 
    <li><a href="http://www.php.cn/">下拉</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="http://www.php.cn/">下拉</a> 
    <ul> 
    <li><a href="#">入门一</a></li> 
    <li><a href="#">入门二</a></li> 
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    <li><a href="#">入门二入门二</a></li> 
    <li><a href="#">入门二入门二入门二</a></li> 
    <li><a href="#">入门二</a></li> 
    </ul> 
</li> 
<li><a href="http://www.php.cn/">下拉</a> 
    <ul> 
    <li><a href="#">基础三</a></li> 
    <li><a href="#">基础</a></li> 
    <li><a href="#">基础三案例三</a></li> 
    <li><a href="#">基础三案例三案例三</a></li> 
    </ul> 
</li> 
<li><a href="http://www.php.cn/">下拉</a> 
    <ul> 
    <li><a href="#">技巧四</a></li> 
    <li><a href="#">技巧四</a></li> 
    <li><a href="#">技巧四</a></li> 
    <li><a href="#">技巧四111</a></li> 
    </ul> 
</li> 
 
<li><a href="http://www.php.cn/">DIV</a> 
    <ul> 
    <li><a href="http://www.php.cn/">p</a></li> 
    <li><a href="#">模板</a></li> 
    <li><a href="#">模板</a></li> 
    <li><a href="#">模板模板</a></li> 
    <li><a href="#">模板模板模板</a></li> 
    <li><a href="#">模板模板</a></li> 
    <li><a href="#">模板模板</a></li> 
    <li><a href="#">模板模板模板模板</a></li> 
    </ul> 
</li> 
<li><a href="http://www.php.cn/">p</a> 
    <ul> 
    <li><a href="http://www.php.cn">DIV</a></li> 
    <li><a href="#">手册</a></li> 
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    <li><a href="#">手册手册</a></li> 
    <li><a href="#">手册手册手册</a></li> 
    </ul> 
</li> 
</ul>

<style type="text/css"> 

*{margin:0;padding:0;border:0} 
body{ font-family: arial, 宋体, serif; 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;font-weight:bold} 
 
#nav li{float: left; width: 80px; background:#CCC} 
#nav li a:hover{ background:#999} 
#nav li ul{line-height: 27px;  list-style-type: none;text-align:left;left: -999em; width: 180px; position: absolute} 
#nav li ul li{float: left; width: 180px;background:#EFEFEF} 
 
 
#nav li ul a{display: block; width: 156px;text-align:left;padding-left:24px; overflow:hidden} 
 
#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: auto} 
#nav li.sfhover ul{left: auto} 
#content{clear: left} 
</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(){
        thisthis.className=this.className.replace(new RegExp("( ?|^)sfhover\\b"), 
"");
        }
    }
}
window.onload=menuFix; 
</script>