Have you noticed a change in your organic search traffic or ranking of the last week, and have a high ratio of ads to content at the top of your web pages, chances are you could be affected by a refresh of the Google page layout algorithm.
Google’s Matt Cutts announced on Twitter that a refresh of the algorithm occurred on February 6, although he didn’t go into any detail on how much of an impact this might have.
Google’s page layout algorithm targets sites that are light on content and heavy on ads “above the fold” (the part of the page visible to a user before scrolling).
At Pubcon in October, Cutts specifically mentioned in his keynote that they were working on the next generation of the page layout algorithm, and specifically targeting sites that have large ads above the fold. He suggested that webmasters should make changes before the new algorithm impacted their sites.