#box1{
  float: left;
  background: green;
  color: white;
  width: 150px;
  height: 700px;
}

#box2{
  float: left;
  background: purple;
  color: white;
  width: 300px;
  height: 700px;
}

#box3{
  float: left;
  background: cyan;
  color: black;
  width: 150px;
  height: 700px;
}