Search Engine Optimization (SEO). Usually, that would find any information on the Internet, enter a keyword in the line of site search engine (Google, Yahoo, Altavista, MSN, etc.). However, not all searching the same issue a list of links to the desired resource. Why so? What are the same criteria selected information online? English has the word search engine optimization, which is more commonly used in the acronym SEO. Translation as optimization (work) search engines. These machines with their search engine optimization techniques and responsibility, a list of useful sites, or not. SEO works with codes, text, structure and external factors site to raise the issue of its search engine. In other words, there are certain techniques, how to have a digital machine surrender site to the top of the list on the subject. But to begin to figure out what a search engine. Search Engine or search engine, looks set parameters for the site and determine the appropriateness of the request. Under the parameters of the site in the first place was the frequency of keywords. Search algorithms produce semantic analysis of the text to search for spam filtering. A search spam is a phenomenon where the keyword appears increasingly certain percentage of the total content on the page. Therefore, optimization, search engines need to work with these internal factors site, as with the demands of the text and layout, the quality and quantity of text, the optimum condition of the structure and navigation page. And to external factors include the exchange of links, your site, recording catalogs and other actions to improve ssylaemosti the resource. At the dawn of the emergence of search engines, search according to the text of the site and some other internal parameters. Owners pages manipulated internal factors, resulting in the surrender of many researchers, the first few pages were landfill sites. This situation drastically reduced the quality of search engines, and led to the decline of many servers. Now used many external factors precluding optimization using only text on the site. However, SEO developed along with search engines. Today, the search results are increasingly found in commercial sites artificially inflated popularity. Founders of such and similar resources are all permitted and prohibited methods of optimization. Roughly, they can be divided into white, gray and black. White called optimization site without formally prohibited by search engines, methods Pop resource. Under gray SEO is partial banned by search engines, methods of moving online. For example, the purchase links from other sites or use linkatorov etc. Black optimization usually presented as dorveev pages created specifically for the search engine robots. The text on these sites can not be read because of the excessive repetition of keywords. Another black SEO method was the use of so-called hidden text. This text invisible to the user, but the search robots easily defined. Usually, hidden text containing keywords to give weight "optimizing" page.