Algorithm
The term search engines use for the formulae they use to determine the rankings of your Natural Listings. Search engines will periodically send a Spider through your website to view all its information. Their programs analyze then analyze this and other data to value your site and fix whether or not, and how high or low pages on your site will appear on various searches. These algorithms can be very complicated (Google alone currently uses 106 different variables) and search engines closely guard their algorithms as trade secrets.