Google’s latest update is known among SEO’s lovingly as the “Mayday update”. The update ended about a week ago and as with any update, there are winners and there are losers. We known that the update was algorithmic and not index-based. Basically, it has to do with the rankings of your site not the pages Google cares about. Reportedly this update went through vigorous testing (we did see some back-and-forths for quite some time prior to the stabilization that occurred last week) and Google likes what they see. There is apparently no need for a “corrective update” to repair what went wrong as (according to Google’s Matt Cutts) the results are better for the update.
The focus in the update was longtail phrases. Rather than try to explain it all I’ll let the horse speak. (this is a reference to “from the horses mouth – not Matt
You can read more from ex-Googler Vanessa Fox at http://searchengineland.com/google-confirms-mayday-update-impacts-long-tail-traffic-43054.
And good luck !