Page layout, using iframes & CSS

this seems like it should be easy, but i cant seem to quite get my head around it. i want to create a page that has a header/navigation bar (nav1) at the top, which loads content into a two colum section below it. the left section (nav2) wil have sub navigation, and load content into the right column (data). the content that will be loaded into “data” will vary in size, so i’ll need it to scroll, and work (as well as possible) with diff screen sizes.

i’ve attached a simple pic, which should explain better than my words, exactly what i mean. (i think it takes a second or so for that admins to review the pic before it shows up… )

since i’m “trying” nowadays to use lots of CSS, i’m hoping to avoid regular frames, and tables to accomplish this. seems like it should be pretty simple… can anybody tell me how to structure this, or know here i can find an example who’s code i can take a peak at?