<!doctype html>
<title>CSS Test Reference</title>
<style>
body { margin: 0 }
.first {
  width: 100px;
  height: 50px;
  background: lime;
}
.space {
  height: 50px;
}
.second {
  width: 100px;
  height: 100px;
  background: lime;
}
</style>
<div class="first"></div>
<div class="space"></div>
<div class="second"></div>