.gnb{}
.gnb ul li{float:left;width:20%;}
.gnb ul li a{position:relative;z-index:10;text-align:center;font-size:21px;color:#fff;}
.gnb ul li a span{display:inline-block;}
.gnb ul li a span:after{content:'';display:block;margin-top:8px;width:100%;height:1px;background:#fff;}