Floated element dieing

hi all,
putting the finishing touches on my portfolio (the ads on my server are screwing up the header a bit)

just wondering, if you resize the browser lengthwise (making it smaller), the content div falls down to below the navigation.
i tried fooling aroundwith the floats and such, but nothing seems to work.
and i can’t use absolute positioning either.

anyone know what the problem is?

thank you (-: