为什么我给li 加一个背景色 会遮住下方的外阴影效果?
.topmenu li{
height: 30px;
line-height: 30px;
background-color:#F8F8F8; /*这是加的颜色*/
font-size: 15px;
list-style-type: none;
text-align: left;
padding-left: 8px;
z-index: 3;
background-image: url(http://img1.sycdn.imooc.com//5411027300014f0200220030.jpg);
background-repeat: no-repeat;
background-position: right;