Edit in JSFiddle

<div class="wrapper1">
  <div class="box1">
  </div>
  <div class="box2">
  </div>
  <div class="box3">
  </div>
</div>

.wrapper1 {
  width: 500px;
  height: 200px;
  background: green;
}
.box1 {
  width: 100px;
  height: 100px;
  background: red;
  float: left;
}
.box2 {
  width: 100px;
  height: 100px;
  background: blue;
  float: left;
}
.box3 {
  width: 100px;
  height: 100px;
  background: yellow;
}