清除float的方法

以下三种方法选一，推荐第三种

<div id="wrapper" class="clearfix">
  <div id="first"></div>
  <div id="second"></div>
  <div class="clear"></div>
</div>

#wrapper {
  overflow: hidden;  /*清除浮动方法一*/
  width:200px;
  border: 1px solid black;
}
#first, #second {
  width:80px;
  height:40px;
  border: 1px solid red;
}
#first {
  float: left;
}
#second {
  float: right;
}
.clear {
 // clear: both; /*清除浮动方法二*/
}
.clearfix::after{
 clear: both;
 content: "";
 display: block;
 height: 0;
 visibility: hidden;
}