SOURCE

<div class="wrap">
  <div class="left">left</div>
  <div class="right">right</div>
  <!-- <div class="clear"></div> -->
</div>

.wrap{
  border: 1px solid red;
  padding:2px;
  /*1*/
  /* height:100px; */
  /*2*/
  /* overflow:hidden; */
  /*3 <div>*/
}

/* .wrap:after{
  display:block;
  content:"";
  clear:both;
  //visibility:hidden;
} */

.left{
  width:49%;
  height:100px;
  border:1px solid green;
  float:left;
}
.right{
  width:49%;
  height:100px;
  border:1px solid green;
  float:right;
}

/* .clear{
  clear:both;
} */