.nav a{display: inline-block; width:100px;  line-height:40px; border:1px solid #ececec;  text-align: center;
  font-size: 12px;}
.nav a:hover{background:url(http://img0.imgtn.bdimg.com/it/u=4098345265,3184037055&fm=21&gp=0.jpg)}