What is Google Caffeine?

What is the difference between Google Mayday and Google Caffeine ?

• Answer:

  Caffeine refers to an infrastructure update that began testing late in 2009 and was rolled out more completely in May-June of 2010. It doesn't specifically change algorithmic/organic results, though it does impact them by providing faster spidering, indexing and processing of the web (and creating a system through which Google is likely considering more temporal-based factors in the ranking weights). Mayday was a specific algorithmic update pushed by the search quality + webspam teams at Google on or about May 1st (I think it's closer to May 3rd based on our data, but it could be propagation across data centers causing that). Mayday specifically impacted the way Google ranks content for long tail queries and appeared to bias against many previously well-performing pages/sites that had little unique content on them and few external links pointing to those deep pages. Some SEOs felt that it substantively changed the way Google considered the concept of "Domain Authority" and how sites that have drawn in many links, trust, authority, etc. can rank their less "quality" pages. On a personal note, this explanation matches well with my experiences and the data/sites we monitor. A more in-depth explanation is here - http://www.seomoz.org/blog/whiteboard-friday-googles-may-day-update-what-it-means-for-you