演示效果截图

CSS代码

<style type="text/css">
body { margin: 0; padding: 0; text-align: center;
background-color: #eee; }
#bd { margin: 20px auto;padding: 5px 20px 20px;
border:1px solid #bbb width:600px;background-color:#9CCE2E;}
#popup {width: 300px;height: 132px;padding: 10px;
position: absolute;left:443px;top:15px;border:1px solid blue;
background-color: #fff;filter:alpha(opacity=60);
opacity:0.4;}
#popup iframe{display:none;
	display:block;
	position:absolute;
	top:0;
	left:0;
	z-index:-1;
	filter:mask();
	width:3000px;
	height:3000px;}
</style>

HTML代码

<div id="bd">
  <h1>让div浮于select之上的完美解决方案</h1>
  <h3>www.v404.cn</h3>
  <div class="parameter">
    <label for="ddTest">下拉框</label>
    <select id="ddTest">
      <option>选项1</option>
      <option>选项2</option>
    </select>
  </div>
</div>
<div id="popup">让div浮于select之上的完美解决方案
  <!--[if lte IE 6.5]><iframe></iframe><![endif]-->
</div>