Search engine optimization (SEO) is the process of improving the volume or quality of traffic to a web site or a web page (such as a blog) from search engines via “natural” or un-paid (“organic” or “algorithmic”) search results as opposed to other forms of search engine marketing (SEM) which may deal with paid inclusion. The theory is that the earlier (or higher) a site appears in the search results list, the more visitors it will receive from the search engine. SEO may target different kinds of search, including image search, local search, video search and industry-specific vertical search engines. This gives a web site web presence.
As an internet marketing strategy, SEO considers how search engines work and what people search for. Search engine optimizers may offer SEO as a stand-alone service or as a part of a broader marketing campaign. The term “search engine friendly” may be used to describe web site designs, menus, content management systems, images, videos, shopping carts, and other elements that have been optimized for the purpose of search engine exposure.
Another class of techniques, known as black hat SEO or spamdexing, uses methods such as link farms, keyword stuffing and article spinning that degrade both the relevance of search results and the user-experience of search engines. Search engines look for sites that employ these techniques in order to remove them from their indices.
Webmasters and content providers began optimizing sites for search engines in the mid-1990s, as the first search engines were cataloging the early web. Site owners started to recognize the value of having their sites highly ranked and visible in search engine results, creating an opportunity for both white hat and black hat SEO practitioners. According to industry analyst Danny Sullivan, the phrase “search engine optimization” probably came into use in 1997.
Early versions of search algorithms relied on webmaster-provided information such as the keyword meta tag, or index files in engines like ALIWEB. Meta tags provide a guide to each page’s content. Inaccurate, incomplete, and inconsistent data in meta tags could and did cause pages to rank for irrelevant searches. Web content providers also manipulated a number of attributes within the HTML source of a page in an attempt to rank well in search engines.
To provide better results to their users, search engines had to adapt to ensure their results pages showed the most relevant search results, rather than unrelated pages stuffed with numerous keywords by unscrupulous webmasters. Graduate students at Stanford University, Larry Page and Sergey Brin, developed “backrub,” a search engine that relied on a mathematical algorithm to rate the prominence of web pages. Page and Brin founded Google in 1998. By 2004, search engines had incorporated a wide range of undisclosed factors in their ranking algorithms to reduce the impact of link manipulation. Google says it ranks sites using more than 200 different signals. The leading search engines, Google and Yahoo, do not disclose the algorithms they use to rank pages. In 2005 Google began personalizing search results for each user. Depending on their history of previous searches, Google crafted results for logged in users. In 2008, Bruce Clay said that “ranking is dead” because of personalized search. In December 2009 Google announced it would be using the web search history of all its users in order to populate search results.
Real-time-search was introduced in late 2009 in an attempt to make search results more timely and relevant.
By 1997 search engines recognized that webmasters were making efforts to rank well in their search engines, and that some webmasters were even manipulating their rankings in search results by stuffing pages with excessive or irrelevant keywords. Early search engines, such as Infoseek, adjusted their algorithms in an effort to prevent webmasters from manipulating rankings.
Due to the high marketing value of targeted search results, there is potential for an adversarial relationship between search engines and SEOs. SEO companies that employ overly aggressive techniques can get their client websites banned from the search results. Some search engines have also reached out to the SEO industry, and are frequent sponsors and guests at SEO conferences, chats, and seminars. Major search engines provide information and guidelines to help with site optimization. Google has a sitemaps program to help webmasters learn if Google is having any problems indexing their website and also provides data on Google traffic to the website.
The leading search engines, such as Google and Yahoo!, use crawlers to find pages for their algorithmic search results. Pages that are linked from other search engine indexed pages do not need to be submitted because they are found automatically. Search engine crawlers may look at a number of different factors when crawling a site. Not every page is indexed by the search engines.
Additionally, a page can be explicitly excluded from a search engine’s database by using a meta tag specific to robots. When a search engine visits a site, the robots.txt located in the root directory is the first file crawled. As a search engine crawler may keep a cached copy of this file, it may on occasion crawl pages a webmaster does not wish crawled. Pages typically prevented from being crawled include login specific pages such as shopping carts and user-specific content such as search results from internal searches. In March 2007, Google warned webmasters that they should prevent indexing of internal search results because those pages are considered search spam.
Cross linking between pages of the same website to provide more links to most important pages may improve its visibility. Writing content that includes frequently searched keyword phrase, so as to be relevant to a wide variety of search queries will tend to increase traffic. Adding relevant keywords to a web page’s meta data, including the title tag and meta description will tend to improve the relevancy of a site’s search listings, thus increasing traffic.
Black hat SEO attempts to improve rankings in ways that are disapproved of by the search engines, or involve deception. International markets
Optimization techniques are highly tuned to the dominant search engines in the target market. The search engines’ market shares vary from market to market, as does the competition. It is largest search engine in most markets, but not in others.