<link href="//netdna.bootstrapcdn.com/bootstrap/3.2.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//netdna.bootstrapcdn.com/bootstrap/3.2.0/js/bootstrap.min.js"></script>
<script src="//code.jquery.com/jquery-1.11.1.min.js"></script>
<div class="responsive-helper">
<span class="label label-danger visible-xs">xs</span>
<span class="label label-warning visible-sm">sm</span>
<span class="label label-info visible-md">md</span>
<span class="label label-success visible-lg">lg</span>
</div>