Google's Ranking Penalty
For at least the last couple of months, there has been some buzz about a ranking penalty imposed by Google. Sites that are being penalized are finding that search phrases for which they ranked near the top are now being ranked for those same phrases on page 4 i.e. position 31 or worse.
A common technique for detecting such a penalty is by performing some searches on Google. An alternative and perhaps more definitive way to detect the penalty is to do what Graywolf did and just check the keyword rankings provided by Google's Webmaster Tools.
Once detected, you'll undoubtedly want to take the necessary steps to get the penalty removed. This, of course, is easier said than done because Google isn't going to provide specifics. Rightly so I might add since that would simply give away too much information about their ranking algorithm. Still, an understanding of what may be going on will help you deal with the problem. To that end, here are some of the comments I've come across from a couple of different sites.
Andy Hagans on Threadwatch says that he's, "beginning to think it's permanent... or at least a very long term." John Andrews, from the same Threadwatch posting suggests that the penalty isn't really an integer value added to a site's existing rank, but rather a signal that knocks a site from the first 3 pages. After which the site ends up at position 31 because it would, under normal circumstances, outrank all the other sites that appear on page 4. Amit Patel jumps in and suggests that the penalty is applied periodically and doesn't affect pages, but keywords. Andy Hagans counters that he's seeing it applied to an entire domain.
Although no specifics are known as to what triggers the penalty, some people feel it is due to poor quality inbound links. And for the most part, people seem to agree that the infraction is a minor one that doesn't warrant a site being de-listed entirely.
If you do manage to figure out what it is about your site that is triggering the penalty, Adam Lasnik of Google recommends that once the adjustment is made, to simply re-submit a re-inclusion request.
Although I like to do SEO-related experiments, I think I'll take a pass on this one!