我是这样写，有问题么？？会不会产生副作用

/*在此定义相关CSS样式*/
.topList {
    width:300px;
    height:180px;
    border:1px solid #E8E8E8;
    margin:0 auto;
}

ul{
    list-style-type: none;
    padding: 0 5px 5px 5px;
    font-size:12px;
}

 em{
    width:20px;
    height:16px;
    text-align:center;
    font-style:normal;
    color:#333;
    background:url("http://img.mukewang.com/53cf0fa20001d3dc00200032.jpg") no-repeat ;
    background-position:0 -16px;
    display:block;
    float:left;
}

.top em{
    color:#FFF;
    background:url(http://img.mukewang.com/53cf0fa20001d3dc00200032.jpg) no-repeat top  center;
}

.topList a:link,.topList a:visited{
    text-decoration: none;
    color: #888;
}

.topList a:hover,.topList a:active{
    text-decoration: none;
    color: #F00;
}