title: Firefox does not set focus to anchor element
body: <p>I have created a <a href="https://webaim.org/techniques/skipnav/#maincontent" rel="nofollow noreferrer">Skip to Content</a> link on my page that skips to a button. In IE and Chrome, the focus is set on the button which allows me to activate it with Enter. In Firefox however, it does not set focus to the button. It seems to be focusing <em>after</em> the button as I need to Shift+Tab (Tab backwards) to get focus on the button.</p>
  
  <pre><code>&lt;a href="#player__button"&gt;Skip to play button&lt;/a&gt;
  
  &lt;button id="player__button"&gt;
    Play
  &lt;/button&gt;
  </code></pre>
  
  <p>I've created a Fiddle <a href="https://jsfiddle.net/chadfawcett/p4t2wv21/5/" rel="nofollow noreferrer">https://jsfiddle.net/chadfawcett/p4t2wv21/5/</a>. You should be able to reproduce the issue by Tabbing to the <strong>Skip to play button</strong> link, hitting <strong>Enter</strong>, which will put focus on the button. In Chrome and IE you can then hit <strong>Enter</strong> repeatedly to have the onclick listener fire.</p>