title: How does position:absolute change element's overlay properties?
body: <p>In the example <a href="http://learnlayout.com/position-example.html" rel="nofollow">here</a>, I notice if you take away the <code>margin-left:200px</code> from the first section element, it expands its width to fully match the container, but it doesn't go below the nav element, which is has <code>position:absolute</code>. Instead, it's overlaid by the nav element, as if it got a lower z-index. Why is that? Aren't both these elements in the flow of the document? So that means they should come one right after the other right, with the section element appearing under the nav element (this happens when I remove the <code>position:absolute</code>)? Why are they overlaid each other instead?</p>