Google is by a country mile the most popular search engine in the world. It's popular because it seems to rank pages so accurately and quickly time and time again. The secret to its success is its top secret Page Rank Algorithm. Google developed its page
S. Pasupathy, G. Goodson, and V. Prabhakaran. SOSP '05: Proceedings of the twentieth ACM symposium on Operating systems principles, page 1--2. New York, NY, USA, ACM, (2005)