A new algorithmic change has been implemented by Google, affectionately know as the May Day update as it happened around 1st May 2010. Matt Cutts explains that the change is not temporary and the update is looking to improve the quality of the SERP’s that is effecting long tail terms opposed to the head of searches.
Cutts explains that this update is independent to Google Caffeine which is preceding at pace. The update is assessing which sites are the best match for long tail queries. No human involvement in this update and it is purely algorithmic.
Is your SEO affected?
Think about your site, do you have a high quality site, good content and make sure that your site can be viewed as an authority for the search query so not matching off topic queries.