In April 2010, Google announced on their Webmaster Central Blog that site speed had been added to their search ranking algorithms, explaining that "faster sites create happy users and that when sites respond slowly, visitors spend less time there."  Shopzilla carried out A/B testing comparing conversions with page load times and found that the faster pages delivered between 7% and 12% more conversions.  Firefox ran similar tests and found a 15% increase in conversions.