清除浮动

// 清除浮动
.clearfix:after {
  content: "\00A0";
  display: block;
  visibility: hidden;
  width: 0;
  height: 0;
  clear: both;
  font-size: 0;
  line-height: 0;
  overflow: hidden;
}
.clearfix {
  zoom: 1;
}