Untitled

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JS Bin huuuu</title>
<style id="jsbin-css">
.caja{
  background-color:green;
  color:#fff;
  text-align:center;
}

.second{
  background-color:pink;
}

.third{
  background-color:aqua;
}
</style>
</head>
<body>

  <div class="caja first">First example</div>

  <div class="caja second">Second example</div>

  <div class="caja third">Third example</div>


<script id="jsbin-source-css" type="text/css">.caja{
  background-color:green;
  color:#fff;
  text-align:center;
}

.second{
  background-color:pink;
}

.third{
  background-color:aqua;
}</script>
</body>
</html>