The Panda update from Google that affected the search engine rankings of a lot of sites has caused a lot of angst among some webmasters as they watch their rankings fall. Everyone is looking for answers. Not a lot of forums appear to have been affected. There has been a lot of discussion at the Google Webmaster Forums about one forum affected with a lot of valuable information in the thread.
Essentially what Google did was, they used their human quality testers to answer a whole lot of questions about sites. The blogged about their questions here. They then developed the Panda modification to the ranking algorithm to try and lower the ranking of the sites that the human testers deemed to be of lower quality.
If your site lost ranking due to this algorithm update means one of two things:
1. The site rally is of low quality
2. The site is giving signals to the ranking algorithm that are interpreted as low quality
If it is (2), then you need to figure out what those signals are. There is plenty of speculation in the SEO community as to what they are. You really need to go through your site and honestly ask yourself the same questions that Google asked their quality raters.
Some valuable resources on the Panda Update:
Your Site’s Traffic Has Plummeted Since Google’s Farmer/Panda Update. Now What?
The Farmer/Panda Update: New Information From Google and The Latest from SMX West
Characteristics of the Google Panda Algorithm
Google Panda Update – Google’s Content Guidance and Jim’s Take
Panda Slaying: How Nature Teaches SEOs to Adapt to Search Algorithm Changes