What we commonly call the Web is really just the surface. Beneath that is a vast, mostly uncharted ocean called the Deep Web.By its very nature, the size of the Deep Web is difficult to calculate. But top university researchers say the Web you know — Facebook, Wikipedia, news — makes up less than 1% of the entire World Wide Web.When you surf the Web, you really are just floating at the surface. Dive below and there are tens of trillions of pages — an unfathomable number — that most people have never seen. They include everything from boring statistics to human body parts for sale (illegally).
http://money.cnn.com/2014/03/10/technology/deep-web/index.html