Relevant fiddle: http://jsfiddle.net/tc05vfee/
<div id="header">
<div class="header-nav"><a id="branding" href="/">Branding</a></div>
<div id="left-nav">
<div class="header-nav"><a href="/global.php">nav item</a></div>
</div>
</div>
It ends up with the #left-nav
and child elements being pushed down a couple pixels.
I'm not sure why the nav item is being pushed down.