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search engine optimisation - (SEO) is the process of improving the volume & quality of traffic to a web site from search engines via "natural" ("organic" or "algorithmic") search results for targeted keywords. Usually, the earlier a site is presented in the search results or the higher it "ranks", the more searchers will visit that site. can also target different kinds of search, including image search, local search, & industry-specific vertical search engines.
As an internet marketing strategy for increasing a site's relevance, considers how search algorithms work & what people search for. efforts may involve a site's coding, presentation, & structure, as well as fixing problems that could prevent search engine indexing programs from fully spidering a site. Other, more noticeable efforts may include adding unique content to a site, ensuring that content is easily indexed by search engine robots, & making the site more appealing to users. Another class of techniques, known as black hat or spamdexing, use methods such as link farms & keyword stuffing that tend to harm search engine user experience. Search engines look for sites that employ these techniques & may remove them from their indexes.
The initialism "SEO" can also refer to "search engine optimisers", a term adopted by an industry of consultants who carry out optimisation projects on behalf of clients, & by employees who perform services in-house. Search engine optimisers may offer as a st&-alone service or as a part of a broader marketing campaign. Because effective may require changes to the HTML source code of a site, tactics may be incorporated into web site development & design. The term "search engine friendly" may be used to describe web site designs, menus, content management systems, URLs, & shopping carts that are easy to optimise.
Webmasters & content providers began optimizing sites for search engines in the mid-1990s, as the first search engines were cataloging the early Web. Initially, all a webmaster needed to do was submit a page, or URL, to the various engines which would send a spider to "crawl" that page, extract links to other pages from it, & return information found on the page to be indexed.The process involves a search engine spider downloading a page & storing it on the search engine's own server, where a second program, known as an indexer, extracts various information about the page, such as the words it contains & where these are located, as well as any weight for specific words & all links the page contains, which are then placed into a scheduler for crawling at a later date.
Site owners started to recognize the value of having their sites highly ranked & visible in search engine results. According to industry analyst Danny Sullivan, the earliest known use of the phrase "search engine optimisation" was a spam message posted on Usenet on July 26, 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 provided a guide to each page's content. But using meta data to index pages was found to be less than reliable because the webmaster's account of keywords in the meta tag were not truly relevant to the site's actual keywords. Inaccurate, incomplete, & inconsistent data in meta tags caused 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.
By relying so much on factors exclusively within a webmaster's control, early search engines suffered from abuse & ranking manipulation. 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. Since the success & popularity of a search engine is determined by its ability to produce the most relevant results to any given search allowing those results to be false would turn users to find other search sources. Search engines responded by developing more complex ranking algorithms, taking into account additional factors that were more difficult for webmasters to manipulate.
Graduate students at Stanford University, Larry Page & Sergey Brin developed "backrub", a search engine that relied on a mathematical algorithm to rate the prominence of web pages. The number calculated by the algorithm, PageRank, is a function of the quantity & strength of inbound links. PageRank estimates the likelihood that a given page will be reached by a web user who randomly surfs the web, & follows links from one page to another. In effect, this means that some links are stronger than others, as a higher PageRank page is more likely to be reached by the random surfer.
Page & Brin founded Google in 1998. Google attracted a loyal following among the growing number of Internet users, who liked its simple design. Off-page factors such as PageRank & hyperlink analysis were considered, as well as on-page factors, to enable Google to avoid the kind of manipulation seen in search engines that only considered on-page factors for their rankings. Although PageRank was more difficult to game, webmasters had already developed link building tools & schemes to influence the Inktomi search engine, & these methods proved similarly applicable to gaining PageRank. Many sites focused on exchanging, buying, & selling links, often on a massive scale. Some of these schemes, or link farms, involved the creation of thous&s of sites for the sole purpose of link spamming.
To reduce the impact of link schemes, as of 2007, search engines consider a wide range of undisclosed factors for their ranking algorithms. Google says it ranks sites using more than 200 different signals. The three leading search engines, Google, Yahoo & Microsoft's Live Search, do not disclose the algorithms they use to rank pages. Notable SEOs, such as R& Fishkin, Barry Schwartz, Aaron Wall & Jill Whalen, have studied different approaches to search engine optimisation, & have published their opinions in online forums & blogs. SEO practitioners may also study patents held by various search engines to gain insight into the algorithms.
By 1997 search engines recognized that some webmasters were making efforts to rank well in their search engines, & even manipulating the page rankings in search results. Early search engines, such as Infoseek, adjusted their algorithms to prevent webmasters from manipulating rankings by stuffing pages with excessive or irrelevant keywords.
Due to the high marketing value of targeted search results, there is potential for an adversarial relationship between search engines & SEOs. In 2005, an annual conference, AIRWeb, Adversarial Information Retrieval on the Web, was created to discuss & minimize the damaging effects of aggressive web content providers.
SEO companies that employ overly aggressive techniques can get their client websites banned from the search results. In 2005, the Wall Street Journal profiled a company, Traffic Power, which allegedly used high-risk techniques & failed to disclose those risks to its clients. Wired magazine reported that the same company sued blogger Aaron Wall for writing about the ban. Google's Matt Cutts later confirmed that Google did in fact ban Traffic Power & some of its clients.
Some search engines have also reached out to the SEO industry, & are frequent sponsors & guests at SEO conferences & seminars. In fact, with the advent of paid inclusion, some search engines now have a vested interest in the health of the optimisation community. Major search engines provide information & guidelines to help with site optimisation. Google has a Sitemaps program to help webmasters learn if Google is having any problems indexing their website & also provides data on Google traffic to the website. Yahoo! Site Explorer provides a way for webmasters to submit URLs, determine how many pages are in the Yahoo! index & view link information.
The leading search engines, Google, Yahoo! & Microsoft, 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. Some search engines, notably Yahoo!, operate a paid submission service that guarantee crawling for either a set fee or cost per click. Such programs usually guarantee inclusion in the database, but do not guarantee specific ranking within the search results. Yahoo's paid inclusion program has drawn criticism from advertisers & competitors. Two major directories, the Yahoo Directory & the Open Directory Project both require manual submission & human editorial review. Google offers Google Webmaster Tools, for which an XML Sitemap feed can be created & submitted for free to ensure that all pages are found, especially pages that aren't discoverable by automatically following links.
Search engine crawlers may look at a number of different factors when crawling a site. Not every page is indexed by the search engines. Distance of pages from the root directory of a site may also be a factor in whether or not pages get crawled.
Main article: Robots Exclusion Standard
To avoid undesirable content in the search indexes, webmasters can instruct spiders not to crawl certain files or directories through the standard robots.txt file in the root directory of the domain. 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. The robots.txt file is then parsed, & will instruct the robot as to which pages are not to be 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 & 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.
SEO techniques are classified by some into two broad categories: techniques that search engines recommend as part of good design & those techniques that search engines do not approve of & attempt to minimize the effect of, referred to as spamdexing. Some industry commentators classify these methods, & the practitioners who employ them, as either white hat SEO, or black hat SEO. White hats tend to produce results that last a long time, whereas black hats anticipate that their sites may eventually be banned either temporarily or permanently once the search engines discover what they are doing.
An SEO technique is considered white hat if it conforms to the search engines' guidelines & involves no deception. As the search engine guidelines are not written as a series of rules or commandments, this is an important distinction to note. White hat SEO is not just about following guidelines, but is about ensuring that the content a search engine indexes & subsequently ranks is the same content a user will see.
White hat advice is generally summed up as creating content for users, not for search engines, & then making that content easily accessible to the spiders, rather than attempting to trick the algorithm from its intended purpose. White hat SEO is in many ways similar to web development that promotes accessibility, although the two are not identical.
Black hat SEO attempts to improve rankings in ways that are disapproved of by the search engines, or involve deception. One black hat technique uses text that is hidden, either as text colored similar to the background, in an invisible div, or positioned off screen. Another method gives a different page depending on whether the page is being requested by a human visitor or a search engine, a technique known as cloaking.
Search engines may penalize sites they discover using black hat methods, either by reducing their rankings or eliminating their listings from their databases altogether. Such penalties can be applied either automatically by the search engines' algorithms, or by a manual site review. One infamous example was the February 2006 Google removal of both BMW Germany & Ricoh Germany for use of deceptive practices. Both companies, however, quickly apologized, fixed the offending pages, & were restored to Google's list.
Eye tracking studies have shown that searchers scan a search results page from top to bottom & left to right (for left to right languages), looking for a relevant result. Placement at or near the top of the rankings therefore increases the number of searchers who will visit a site. However, more search engine referrals does not guarantee more sales. SEO is not necessarily an appropriate strategy for every website, & other Internet marketing strategies can be much more effective, depending on the site operator's goals. A successful Internet marketing campaign may drive organic traffic to web pages, but it also may involve the use of paid advertising on search engines & other pages, building high quality web pages to engage & persuade, addressing technical issues that may keep search engines from crawling & indexing those sites, setting up analytics programs to enable site owners to measure their successes, & improving a site's conversion rate.
SEO may generate a return on investment. However, search engines are not paid for organic search traffic, their algorithms change, & there are no guarantees of continued referrals. Due to this lack of guarantees & certainty, a business that relies heavily on search engine traffic can suffer major losses if the search engines stop sending visitors. It is considered wise business practice for website operators to liberate themselves from dependence on search engine traffic. A top ranked SEO blog SEOmoz.org has reported, "Search marketers, in a twist of irony, receive a very small share of their traffic from search engines." Instead, their main sources of traffic are links from other websites.
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