1.opacity:0.5;(半透明效果在ie9及以上版本适用，ie8及以下不兼容)

解决办法：在css中加入filter: progid:DXImageTransform.Microsoft.Alpha(opacity=50);即可

eg:  .fb_xl li{

       font-size:16px; color:#FFF; width:230px;  line-height:35px;

       background:#66cc97  center repeat; opacity:0.5; list-style:none;  z-index: 9999;

       filter: progid:DXImageTransform.Microsoft.Alpha(opacity=50);

}

ie8兼容半透明效果css