The criterion in this case one – is how the site meets the search request a person searches for information on the Internet. For example, someone enters a search phrase "buy a bike 'and find dozens of sites responding to this request. In this case, indeed, those that were in the first positions, indicate where and how to buy a bike. The others, more and less consistent with this theme. This ranking was the result of the search engines with the help of robotic spiders several previously collected information on all existing sites. They defined their quality, the subject of the whole site and individual pages in particular. This process of gathering information about the sites is called indexing, and means that Information on the Internet resource is already in the database search engine. Now, searchers found the man who seeks the most appropriate resources for him so he could make his choice. Gathering information about the sites and enters them into its database is the most important factor in promoting websites, as indexing sites – is a guarantee that the search engines will come to you people, but statistically, it is thus achieved most traffic. Attract visitors from search engines – this is the cheapest and most effective way to increase site traffic. If you understand this circuit, it becomes evident that, since on the site will be a key word or phrases, but in this case, 'buy a bike', then no one would ever purposely not get to your site for that term. .