position与z-index的关系

.simulationgame .gameranking .rankinginfo
{
140px;
margin:0 auto;
font-family:Arial, Microsoft YaHei;
font-size:14px;
color:#8c8b8b;
text-align:center;
background:#fff;
z-index: 10;
position: relative;
}

.simulationgame .gameranking .line
{
100%;
height:1px;
background-color:#8c8b8b;
position: relative;
top: -8px;
}

好像把两个div的position改成一样，然后用z-index控制显示层就行了，改日有时间好好研究下！