title: Use of em for headers
body: <p>I'm new to the use of em. I've always used px so far but it's time to move on.
  I'm stuck with my headers. I've got an H2 and an H6 with the same styling</p>
  <pre><code>font-size:1.2em;
  line-height:1.2em;
  </code></pre>
  <p>When I put both headers in the same parent element they are displayed in a different size. How is that possible? Are they relative to the parent or are they relative to the default font-size of themselves.</p>
  <p><a href="http://jsfiddle.net/SBAHa/1" rel="nofollow noreferrer">http://jsfiddle.net/SBAHa/1</a></p>