Robert_Charlton - 8:22 pm on Apr 11, 2011 (gmt 0)
grimmer - Your quote about feedback signals is from the official Google announcement. I'm including the first two paragraphs of the article.
To confirm answers already posted, the second paragraph contains some comments about the signals. User blocking jumps out, and I've emphasized it in the excerpt below....
High-quality sites algorithm goes global, incorporates user feedback
Monday, April 11, 2011 at 12:00 PM
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....