There are two commonly used, simple techniques, each of which have their pros and cons:[list=1][*]Float the navigation section left, and set a left margin on the content section to make room.
Pro: works with any combination of longer content, shorter nav or vice versa.
Con: nav must be before content in the source: bad for text browsers and screen readers, bad for search engines.[*]Aboslutely position the navigation in the top left corner of a wrapper around the content an navigation sections; again, use left margin to create room.
Pro: nav can be behind the content: good for text browsers, etc.
Con: nav can never be longer than the content or it will spill over the footer.[/list=1]
There are dozens more, but you'll really have to do some digging; try the sticky on top of the forum.
Read this article on Mezzoblue: Friday challenge
; it decribes an alternative with all floats and
the correct source order!