Search Engines love good content. Site and navigation structure are important but ulimately without succint relevant content, copywritten carefully to avoid the repetative use of the same words, which may be construded by Google Yahoo etc as spamming.
I came across web site WritingWebWords.com
on http://del.icio.us/tag/css. A near perfectlly optimised site, maybe the page titles need a bit of work but that’s probably a moot point