Edit in JSFiddle

<div class="father">
  <div class="left">左</div>
  <div class="right">右</div>
</div>

html,
body {
  margin: 0;
  padding: 0;
}
.father .left,
.father .right {
  height: 200px;
  line-height: 200px;
  text-align: center;
}
.father .left {
  float: left;
  width: 200px;
  background-color: #FAD7F0;
}

.father .right {
  margin-left: 200px;
  background-color: #C7DAFC;
}