jQuery实现简单二级下拉菜单

<div class="UpLayer">
<dl>
<dt>
<a href="javascript：void(0)">phpstudy</a></dt>
<dd>
<a href="http://www.demo.com/js/">特效</a> <a href="http://www.demo.com/Tutorials/">教程</a> <a href="http://www.demo.com/zy/">资源</a> <a href="http://www.demo.com/mb/">模板</a> <a href="http://www.demo.com/news/">资讯</a></dd>
</dl>
</div>

<script type="text/javascript"> 
// 【经典】弹出层菜单 
$(document).ready(function(){ 
  var objStr = ".UpLayer"; 
  $(objStr).each(function(i){ 
    $(this).click(function(){ 
      $($(objStr+" dd")[i]).show(); 
      $($(objStr+" dt")[i]).addClass("UpLayer02"); 
    }); 
    $(this).hover(function(){},function(){ 
      $($(objStr+" dd")[i]).hide(); 
      $($(objStr+" dt")[i]).removeClass("UpLayer02"); 
    });  
  }); 
}); 
</script> 

body,h1,h2,h3,h4,h5,h6,p,ol,ul,li,dl,dt,dd{padding:0;margin:0;} 
li{list-style:none;} 
img{border:none;} 
u{text-decoration:none;} 
em{font-style:normal;} 
a{color:#424242;text-decoration:none;outline:none;blr:expression(this.onFocus=this.blur());} 
body{font-size:12px;font-family: Arial,Verdana, Helvetica, sans-serif; word-break:break-all;} 
.box{margin:0 auto;text-align:left;width:920px;} 
.clear{clear:both;} 
/* 【经典】弹出层菜单 */ 
.UpLayer{ margin:100px;} 
.UpLayer dl dt{width:50px;position:absolute; z-index:3;padding:0 5px;line-height:20px;} 
.UpLayer02{border:#ccc 1px solid; border-bottom:none;background:#f1f1f1; margin:-1px 0 0 -1px;} 
.UpLayer dl dd{ width:80px;position:absolute;z-index:2;border:#ccc 1px solid;padding:5px; line-height:20px; background:#f1f1f1; display:none; margin:19px 0 0 -1px;} 
.UpLayer dl dd a{ display:block;border-bottom:#ccc 1px dashed;}