清除浮动的2中方式

.clear-fix::after {
  clear: both;
  content: '';
  display: block;
  width: 0;
  height: 0;
  visibility: hidden;
}

.clear-fix {
  *zoom: 1;
}

.clear-fix::before,
.clear-fix::after {
  content: "";
  display: table;
}

.clear-fix::after {
  clear: both;
}

.clear-fix {
  *zoom: 1;
}