This works fine to have the two columns (navigation on left, all content on right).
BUT - in the main content, I often have to float elements which means that I also have to clear them. But when I clear anything, it drops below leftNav. Check out the screenshot if it's unclear what I'm talking about.
I've tried a million different things, including adding float:none; to the mainConent div, but nothing I do works. Does anyone have any ideas?