SEO Who do you trust?:
Internet search engines exist to organize the seemingly immeasurable amount of information available on the web. They direct people to pages that are relevant to their searches, pages that discuss the exact keywords they are looking for. For businesses that receive the majority of their clientele from search engines, search engine rankings can make or break their business.
Search engine optimization (SEO) is a marketing technique that enhances a website and its content in order to increase the chances of achieving a high rank the search engine result pages (SERPs). Search engines are very secretive about their criteria and ranking systems as they continuously update and revise their algorithms (mathematical formulas used to determine which web pages are displayed in search results), and therefore there is less likelihood of webmasters and search engine optimizers being able to achieve higher rankings by manipulation and spamming.
Every search engine has its own formula and criteria for indexing and ranking pages. One can analyze SERPs and backward links (all the links pointing at a particular web page) and attempt to determine a search engine's indexing criteria, however there's a lot of risk involved in relying on a limited number of optimization techniques.
Because of the unpredictable nature of search engines, websites can easily move from a top ranking position on a SERP down to the third or fourth SERP or even be banned from the search engine altogether.