1:  <style type="text/css">

   2:  <!--

   3:  body{

   4:      margin:0;

   5:      padding:0;

   6:      background-color:#FFFFFF;

   7:  }

   8:  .alpha1,.alpha2{

   9:      width:100%;

  10:      height:auto;

  11:      min-height:250px;/* 必需 */

  12:      _height:250px;/* 必需 */

  13:      overflow:hidden;

  14:      background-color:#FF0000;/* 背景色 */

  15:  }

  16:  .alpha1{

  17:      filter:alpha(opacity=20); /* IE 透明度20% */

  18:  }

  19:  .alpha2{

  20:      background-color:#FFFFFF;

  21:      -moz-opacity:0.8; /* Moz + FF 透明度20%*/

  22:      opacity: 0.8; /* 支持CSS3的浏览器（FF 1.5也支持）透明度20%*/

  23:  }

  24:  .ap2{

  25:      position:absolute;

  26:  }

  27:  -->

  28:  </style>

   1:  <!--S Demo-->

   2:  <div class="alpha1">

   3:    <div class="ap2">

   4:    <p>背景为红色(#FF0000)，透明度20%。</p>

   5:    </div>

   6:    <!--[if IE]><![if !IE]><![endif]--> <div class="alpha2"></div> <!--[if IE]><![endif]><![endif]-->

   7:  </div>