Early May we reported on a possible Google Update coined the Google MayDay update. Now, I know Google wanted examples of sites claiming they were hit, so here you go, SEOmoz said they were impacted by MayDay.
What is MayDay, well - a lot of sites are claiming they lost rankings in Google for their long tail keywords, which resulted in a drop of traffic of about 10 - 20% or more. Now, with the launch of new Google design some are blaming that for a Google referrer drop but some noticed it before the redesign.
A new WebmasterWorldthread started on the topic, the second one on this topic. We have some smart SEOs and webmasters formulating ideas and theories, some of you who may disagree with them, but I will document them here anyway.
Tedster believes that what we are witnessing over at Google now may be a "automated, and self-improving algorithm" deployed by Google. Possibly part of how Google indexes content with "un-launched" Google Caffeine update. He explains:
There is a lot going on with Google and we may need to approach the Google SERPs from an entirely different model than the "data set" concept that we've been using in recent times. I'm currently thinking of something more along the lines of waveforms and continuous statistical testing... with near-real-time adjustments and experimentation in a kind of feedback loop. Something like automated algorithm evolution.
Rand from SEOmoz also formulated some theories, which he posted in his video.
I really think Google needs to do a blog post about what is going on or not going on soon. Between Caffeine, the new design and this - there is just so much confusion out there. Today's Google should not be like this, their communication has been outstanding but when it comes to this topic - it is like they are hiding something.
Forum discussion at WebmasterWorld. Update: After this post, a bunch of us at Search Engine Land decided to get Google on the record on the May Day update. We got them to confirm this is a change to the ranking algorithm and not a change to indexing or crawling. Vanessa Fox wrote it up and goes into more detail there. Here is a quote:
Last week at Google I/O, I was on a panel with Googler Matt Cutts who said, when asked during Q&A, ”this is an algorithmic change in Google, looking for higher quality sites to surface for long tail queries. It went through vigorous testing and isn’t going to be rolled back.”
I asked Google for more specifics and they told me that it was a rankings change, not a crawling or indexing change, which seems to imply that sites getting less traffic still have their pages indexed, but some of those pages are no longer ranking as highly as before. Based on Matt’s comment, this change impacts “long tail” traffic, which generally is from longer queries that few people search for individually, but in aggregate can provide a large percentage of traffic.
Update 2: Matt Cutts of Google posted a video on this topic, watch the May Day Video on our blog.