after加线(:after加下划线)

    .underline{ position:relative; }

    .underline:after {

     position: absolute;

     bottom: 0;

     left: 20px;

     right: 20px;

     height: 1px;

     content: '';

     -webkit-transform: scaleY(.5);

     transform: scaleY(.5);

     background-color: #e3e5e9;              //这个是唯佳的线颜色

    }

    .underline:last-child:after{    //可以这样用

        height:0;

    }