.menu_a{ width:980px; height:33px;}
 .menu_a li{ position:relative;
 margin-left:0px;
  width:85px;
  height:33px;
  line-height:33px;
   font-size:14px; font-weight:bold;

 text-align: center;
 cursor:pointer;
  display:inline;
}
/* Fix IE. Hide from IE Mac \*/
* html ul li { float: left; height: 1%; }
* html ul li a { height: 1%; }
/* End */
 .menu_a li ul{  position: absolute;
  left:0px; /* Set 1px less than menu width */
  top:30px;
  display: none; }
 .menu_a li ul li{}
  .menu_a li ul li a{font-size:12px; font-weight: normal; margin-left:20px; height:30px; line-height:40px; display:block; }
.menu_a li:hover ul, li.over ul { display: block; }

还有个js，IE6下要用这个js显示二级导航，

<script>
startList = function() {
if (document.all&&document.getElementById) {
navRoot = document.getElementById("nav");
for (i=0; i<navRoot.childNodes.length; i++) {
node = navRoot.childNodes[i];
if (node.nodeName=="LI") {
node.onmouseover=function() {
this.className+=" over";
}
node.onmouseout=function() {
this.className=this.className.replace(" over", "");
}
}
}
}
}
window.onload=startList;
</script>

高手能不能帮我看下啊，我都试了很多次了，就是出不来二级导航，用静态测试是能出来，加上SQL就出不来了，不知怎么回事，太急人了