*{
            padding:0;
            margin:0;
            font-size:12px;
        }
        .topList{
            width:300px;
            height:150px;
            border:1px solid #8e8e8e;
            margin:0 auto;
        }
        li{
            list-style-type:none;
            padding:5px;
        }
        a{
            text-decoration: none;
        }
        em{
            width:20px;
            height:16px;
            text-align:center;
            float:left;
            color:#333;
            display:block;
            font-style:normal;
            background-image: url(http://img1.sycdn.imooc.com//53cf0fa20001d3dc00200032.jpg);
            background-position:0px 16px;/*定位图片*/
        }
        .top em{
            background-image: url(http://img1.sycdn.imooc.com//53cf0fa20001d3dc00200032.jpg);
            background-position:16px 0px;
        }
        .ui a:link,a:visited{
            color:#000000;
        }
        .ul a:hover,a:active{
            color:red;
        }