From ICT4D Wiki
http://www.worldwidewebsize.com/
Estimates the total number of existing web pages world wide.
The estimated minimal size of the indexed World Wide Web is based on the estimations of the numbers of pages indexed by Google, Windows Live Search (Msn Search), Yahoo Search and Ask. From the sum of these estimations, an estimated overlap between these search engines is subtracted. The overlap is an overestimation; hence, the total estimated size of the indexed World Wide Web is an underestimation. Since the overlap is subtracted in sequence, starting from one of the four search engines, several orderings (and total estimations) are possible. We present two total estimates, one starting with Yahoo (YGMA) and one starting with Google (GYMA). The figure reported at the top of the page refers to the YGMA estimation.
