图片上方有图片的问题

css:.logout em {
    background: rgba(0, 0, 0, 0) url("../imges/group.png") no-repeat scroll -170px -52px;
    color: #fff;
    display: block;
    font-size: 10px;
    height: 30px;
    left: -20px;
    line-height: 20px;
    position: absolute;
    text-align: center;
    top: -41px;
    width: 60px;
}

html: <div class="user-bar">

                        <ul class="user">
                        <li  class="shape1"><a href=""></a></li>
                        <li  class="shape2"><a href=""></a></li>
                        <li  class="shape3"><a href=""><em>2</em></a></li>
                        </ul>

                      </div>