伪类before和after

伪类before和after

 .one {        font-size: 50px;        color: red;      }      .one::before {        /*content必须填写，有没有值无所谓*/        content: "";        color: green;      }      .one::after{        content: "after";        color: purple;      }<div class='one'>伪类</div>

清除浮动

 .clearfix::before,      .clearfix::after {        content: "";        clear: both;        display: block;      }