Exercise v1.3

<!DOCTYPE html>
<html lang="en">
<head>
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css">
  <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.2/jquery.min.js"></script>
  <script src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>
</head>
<body>

<div class="container">          
  <button type="button" class="btn btn-primary btn-lg">Button</button>
  <button type="button" class="btn btn-primary btn-md">Button</button>
  <button type="button" class="btn btn-primary btn-sm">Button</button>
  <button type="button" class="btn btn-primary btn-xs">Button</button>
</div>

</body>
</html>
Exercise:
