The order in which these millions of results are returned depends on their rela‐tive relevance to your query. In short, Google aims to return the most relevant results first, and the least relevant last. The calculation of this relevance is of ut‐most importance to web site developers and optimizers.
In order to determine a page’s rank for a specific query, two main criteria are used by all major search engines:
1. Keyword relevance: how central is the search term to the theme or meaning of the content on the page?
2. Page trust: how popular and trusted is the page on which the term appears?
These criteria are further broken down into over 200 individual factors, and search engines conceal their exact algorithms from users and webmasters in or‐der to avoid manipulation and spamming.