菜单下拉条

最近，用到了一些js的知识，稍微复习了下，还把之前写的js代码又复习了一遍，这里贴上来！
<!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" lang="zh-CN">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>菜单下拉条</title>

<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; margin:100px 400px;
}

#nav a {
 display: block;  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;  80px; background:#CCC; 
}
#nav li a:hover{
 background:#999;
}
#nav li ul {
 line-height: 27px;  list-style-type: none;text-align:left;
 left: -999em;  180px; position: absolute;
}
#nav li ul li{
 float: left;  180px;
 background: #F6F6F6;
}


#nav li ul a{
 display: block;  165px;_ 180px;height:auto; margin:0 auto;text-align:left; padding-left:15px;
}

#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><!--//--><![CDATA[//><!--
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>
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