Search engines use algorithms to calculate and rank site importance. These algorithms change constantly and are designed to promote websites that give true value to visitors based on search terms.

Bruce Clay, CEO of leading SEO firm Bruce Clay Inc., suggests that there are about 106 variables in the Google algorithm. But he can’t be too sure. “We can come up with a reasonably complete list,” said Clay, “Perhaps 60 to 80 of the variables used to rank sites. However, the full list remains as secretive as the ending of the ‘Da Vinci Code’.”

A search engine’s algorithm is its “special sauce” and the heart of its competitive advantage, so they’re kept very secret. Never believe an SEO Vendor who tells you know they “know” how a search engine algorithm works; all experts in the field make inferences from looking at cause and effect relationships between page content and search results.