title: What's the tabindex="-1" in bootstrap for
body: <p>What's the <code>tabindex</code> attribute in Bootstrap 3 for?</p>
  <p>Its documentation doesn't say anything about them although they use them practically in all modals.</p>
  <p>I've only find this regarding its use, which doesn't really say much</p>
  <blockquote>
  <p><strong>Accessible tooltips for keyboard and assistive technology users</strong></p>
  <p>For users navigating with a keyboard, and in particular users of assistive technologies, you should only add tooltips to keyboard-focusable elements such as links, form controls, or any arbitrary element with a tabindex=&quot;0&quot; attribute.</p>
  </blockquote>
  <p>And I found out <a href="https://github.com/twbs/bootstrap/issues/4854" rel="noreferrer">I can't press <code>esc</code> to hide a modal if the <code>tabindex</code> attribute is not <code>-1</code></a>.</p>
  <ul>
  <li><a href="http://jsfiddle.net/Lz5c1v8d/" rel="noreferrer">Modal closing after pressing <code>esc</code> key (with tabindex)</a></li>
  <li><a href="http://jsfiddle.net/Lz5c1v8d/1/" rel="noreferrer">Modal not closing after pressing <code>esc</code> key (without tabindex)</a></li>
  </ul>