I have noticed many high traffic and/or new and popular websites use a gray background. Websites such as Gmail, Google+, Facebook, Instagram, Yahoo, LinkedIn, Vine and many others all seem to use variations and shades of gray with white foregrounds.
Since this pattern is so common I am wondering if there is a specific reason it is being used such as for visibility, organization or familiarity? And if so are there any other patterns/colors that can pull off the same effect?