Source: http://lifehacker.com/5514997/site-speed-now-a-factor-in-google-rankings
Google announced in an official blog post that, a few weeks back, they began considering site response speed in a web page's ranking in search results. Google has been all about speed for some time, but this subtle introduction could eventually mean big things for sites that put a priority on swift loading—and for those that don't seem to care at all. Right now, the speed ranking only effects fewer than one percent of search queries, Google reports, and only those in English through the Google.com page. [Official Google Blog via Search Engine Watch]