I'm guessing (hoping) there is a good reason that the DIVs in the Zen theme are in reverse order.
In "Main", the natural order should be Banner, Navigation, Content. Instead the template is rendering them backwards and then using CSS to re-order them in the correct position.
Why? It is causing me massive grief.
I should point out that the "Banner" DIV is my own customization of the theme. It actually shows up in the correct natural order. So - really the issue is why is Content rendered BEFORE Navigation? Doesn't make logical sense; is there a technical reason?