title: width and height doesn't seem to work on :before pseudo-element
body: <p><a href="http://jsfiddle.net/C7rSa/">Here</a> is a fiddle.</p>
  
  <pre><code>&lt;p&gt;foo &lt;a class="infolink" href="#"&gt;bar&lt;/a&gt; baz&lt;/p&gt;
  </code></pre>
  
  <p>and</p>
  
  <pre><code>a.infolink::before
  {
      content: '?';
      background: blue;
      color: white;
      width: 20ex;
      height: 20ex;
  }
  </code></pre>
  
  <p>The '?' appears but clearly does not have 20ex size. Why not? Tested in Firefox and Chrome.</p>