水平线加小箭头的效果

    
    
    
 body{
     margin: 0;
     padding: 0;
 }
 .content{
     position: relative;
     width: 100%;
     height:200px;
     border-bottom:2px #000 solid;
 }
 .tag em{
     display: block;
     border-width: 20px;
     position: absolute;
     bottom: -40px;
     left:50%;
     transform:translateX(-50%);
     border-style: solid;
     border-color: #000 transparent transparent;
     font-size: 0;
     line-height: 0;
     z-index:1000;
 }
 .tag span{
     display: block;
     border-width: 20px;
     position: absolute;
     bottom: -36px;
     left:50%;
     transform:translateX(-50%);
     border-style: solid;
     border-color: #fff transparent transparent;
     font-size: 0;
     line-height: 0;
     z-index:1000;
 }