title: Element inside button does not fire click event in Firefox
body: <p><a href="http://jsfiddle.net/dpsr4dkr/" rel="nofollow">This</a> fiddle works in Chrome, but not Firefox. Anyone know why?</p>
  
  <p>Here is the markup:</p>
  
  <pre><code>&lt;button&gt;
      &lt;span onclick="alert('yoo')"&gt;hey&lt;/span&gt;
  &lt;/button&gt;
  </code></pre>