Google Analytics announced over the weekend a change to the definition of a session. It's a small change that supposedly wouldn't have a large impact, however, many webmasters are reporting wild shifts in the following: New vs. Returning direct traffic from non-human browsers (bots) and 15-20% shifts in unique visitors pageviews remain unaffected. http://analytics.blogspot.com/2011/08/update-to-sessions-in-google-analytics.html