title: Modal backdrop not shown using Bootstrap modal
body: <p>I am using the <em>modal</em> plugin from Bootstrap and for some reason the <em>backdrop</em> is not showing. </p>
  
  <p>When I <a href="http://www.w3schools.com/bootstrap/tryit.asp?filename=trybs_ref_js_modal&amp;stacked=h" rel="nofollow noreferrer">check same code on W3Schools</a> I notice a <code>div</code> is generated every time a modal opens:</p>
  
  <pre><code>&lt;div class="modal-backdrop fade in"&gt;&lt;/div&gt;
  </code></pre>
  
  <p>I got the exact same code as on W3Schools but this <code>div</code> is not generated on my site. </p>
  
  <p>How can I fix that?</p>