Have you been finding it harder to build a site that is good with the search engines and with PPC? Had a discussion with a close friend and we feel that Google Adwords is moving away from thin sites. Thin sites worked well in the past, but if we want to build a site that lasts, then it needs to be one that gives value to its visitors.
If you ever explored with Google Analytics, you notice that there is a term called "Bounce Rate". A high bounce rate is not good for your site. This means to say that it will be difficult to rank high in SEO if visitors don't stay for long and click the back button quickly.
There're some sites I've seen that have a good interface that encourages users to stay and explore. A good style is the CSS style, where the header and site pages are kept while the main page changes. Easy navigablity is important for the simple reason that if information is buried deep within a site and users cannot reach it, then such information, is of no use to its readers and the bounce rate will stil be high, not to mention the google bot probably cannot index that info as well.
Implementing a site map, can improve the visibility of your site.
A site map is basically links all the pages within your site to a single page. Once the google bot goes to this page, it will then explore all relevant pages from this site, helping your good info be seen by your targeted audience.
Some of the best sites I've seen are authority niche sites that not only are well monetised, they have a great way of sharing good information as well and makes you wanna stay and explore everything.
All the best!