让div浮于select之上

 1 <style type="text/css">
 2 body {
 3     margin: 0;
 4     padding: 0;
 5     text-align: center;
 6     background-color: #eee;
 7  }
 8 #bd {
 9     margin: 20px auto;
10     padding: 5px 20px 20px;
11 border:1px solid #bbb width:600px;
12     background-color:#9CCE2E;
13 }
14 #popup {
15     width: 300px;
16     height: 132px;
17     padding: 10px;
18     position: absolute;
19     left:443px;
20     top:15px;
21     border:1px solid blue;
22     background-color: #fff;
23     filter:alpha(opacity=60);
24     opacity:0.4;
25 }
26 #popup iframe {
27     display:none;
28     display:block;
29     position:absolute;
30     top:0;
31     left:0;
32     z-index:-1;
33     filter:mask();
34     width:3000px;
35     height:3000px;
36 }
37 </style>

 1 <div id="bd">
 2   <h1>让div浮于select之上的完美解决方案</h1>
 3   <h3>www.php0731.cn</h3>
 4   <div class="parameter">
 5     <label for="ddTest">下拉框</label>
 6     <select id="ddTest">
 7       <option>PHP项目</option>
 8       <option>PHP教程</option>
 9     </select>
10   </div>
11 </div>
12 <div id="popup">让div浮于select之上的完美解决方案
13   <!--[if lte IE 6.5]><iframe></iframe><![endif]-->
14 </div>