title: Fixed navigation div (no height) without overlap
body: <p>I'm trying to <code>position: fixed;</code> a navigation bar at the top of the page (no scrolling), but the first div below is overlapping (see <a href="http://jsfiddle.net/sexyzane/c0wop7vn/" rel="nofollow">http://jsfiddle.net/sexyzane/c0wop7vn/</a> : you can't see the first row of content).</p>
  
  <p>I know the "classic" solution, but I <strong>can't neither force the height of the element</strong>, nor use a pixel-based margin (or padding). Javascript is not an option (I need pure CSS or HTML).</p>
  
  <p>I can't believe is so hard to say "stay at the top, no matter your height, everything else should follow below"...</p>