Google Panda Update

Over a month ago we introduced an algorithmic improvement designed to help people
find more high-quality sites in search. Since then we've gotten a lot of positive responses about the change: searchers are finding better results, and many great publishers are getting more traffic.

Today we've rolled out this improvement globally to all English-language Google users, and we've also incorporated new user feedback signals to help people find better search results. In some high-confidence situations, we are beginning to incorporate data about the sites that users block into our algorithms. In addition, this change also goes deeper into the "long tail" of low-quality websites to return higher-quality results where the algorithm might not have been able to make an assessment before. The impact of these new signals is smaller in scope than the original change: about 2% of U.S. queries are affected by a reasonable amount, compared with almost 12% of U.S. queries for the original change.

Based on our testing, we've found the algorithm is very accurate at detecting site quality. If you believe your site is high-quality and has been impacted by this change, we encourage you to evaluate the different aspects of your site extensively. Google's quality guidelines provide helpful information about how to improve your site. As sites change, our algorithmic rankings will update to reflect that. In addition, you're welcome to post in our Webmaster Help Forums. While we aren't making any manual exceptions, we will consider this feedback as we continue to refine our algorithms.

We will continue testing and refining the change before expanding to additional languages, and we'll be sure to post an update when we have more to share.

Official Google Webmaster Central Blog: High-quality sites algorithm goes global, incorporates user feedback