title: bootstrap progress bar not showing when code is run
body: <p>i have the following and i expected the progress to show on  the background, but nothing shows</p>
  
  <pre><code>&lt;DOCTYPE html&gt;
  &lt;html&gt;
  &lt;body&gt;
      &lt;div class="progress progress-striped"&gt;
        &lt;div class="progress-bar progress-bar-success" role="progressbar" aria-    valuenow="40" aria-valuemin="0" aria-valuemax="100" style="width: 40%"&gt;
        &lt;/div&gt;
      &lt;/div&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>