The Google Panda Update explained

On February 25, 2011 Google rolled out its largest algorithmic update since 2009, dubbed Google Panda Update. Reiterating their aim to provide the most relevant answers to their queries as quickly as possible, Google cited that the main purpose of the update was to remove low-quality shallow sites, namely content farms and sites overloaded with ads.

"This update is designed to reduce rankings for low-quality sites - sites which are low-value add for users, copy content from other websites or sites that are just not very useful. At the same time, it will provide better rankings for high-quality sites - sites with original content and information such as research, in-depth reports, thoughtful analysis and so on."

Removing these shallow sites was meant to allow the top spots to be filled by quality, relevant sites. However, according to a recent article on Wired.com, Google Panda affected 11.8% of all search results, seriously affecting the rankings and traffic of some quality sites.

So how exactly does the Panda Update distinguish bad sites from good sites? An edited transcript of an interview between Stephen Levy and Google's Matt Cutts and Amit Singhal on Wired.com answered this question. In short, Google automated a screening process that examines websites that contains original information and compares it to those sites that contain duplicate, low-quality or irrelevant content. In developing this process, Google also used external testers who reviewed a number of sites.

While some quality sites have taken a blow after the Panda Update rollout, Google maintains that the update will reduce the ranking of sites that don't contain useful content.
What can you do to protect your site? Keep it fresh with original, valuable and authoritative content through and through.