Affiliate sites have been impacted by Google's Panda algorithm changes, perhaps even more so than direct or parent sites. A thin affiliate—defined by Search Engine Watch as an affiliate site that doesn't produce valuable online content–is particularly in Google's sites right now, SEW says.

Some markers to watch for, it advises:

Any site with many visitors that click on it and then immediately return to search results. That tells Google that the site isn’t relevant to the query, says SEW. "Check your analytics to see which pages have the highest bounce rate and work on making them more valuable."

Any site that is blocked by a large number of users.

Sites with a high ratio of ads to content. To play it safe, keep ads to a reasonable level and keep them below the fold, SEW says.

Dealer Sites Too

Dealer sites also seem to be taking a hit from Panda, according to Auto Management Online.  Besides making sure content is fresh and original, dealers should permanently re-direct weak pages to the parent category page, Reg Rix, managing director of Netcars.com, tells the publication. Or better yet, “simply increase the uniqueness of each page with images, videos and useful data.”

A Guide to Better Auto Content

To gauge such efforts, sites might want to refer to the J.D. Power and Associates 2011 Manufacturer Website Evaluation Study Wave. In addition to providing new vehicle shoppers with adequate information that is easy to access, the most useful automotive brand websites also provide a consistently satisfying experience across all points of entry, including the home page and model-level pages, it found.

Honda ranked highest with a score of 836 on a 1,000-point scale, and performs particularly well in the information/content, navigation and speed measures.