<style>
.container {
  background-color: green;
  width: 200px;
  height: 200px;
}

.float {
  float: left;
  background-color: blue;
  height: 100px;
  width: 300px;
}
.overflow {
  width: 0px;
  height: 0px;
  overflow: hidden;
  outline: 5px solid cyan;
}
</style>
<div class=container>
  <div class=float></div>
  <div class=overflow></div>
</div>
