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(SEO) as a subset of search engine marketing seeks to improve the number and quality of visitors to a web site from "natural" ("organic" or "algorithmic") search results. The quality of visitor traffic can be measured by how often a visitor using a specific keyword leads to a desired conversion action, such as making a purchase or requesting further information. In effect, SEO is marketing by appealing first to machine algorithms to increase search engine relevance and secondly to human visitors. The term SEO can also refer to "search engine optimizers", an industry of consultants who carry out optimization projects on behalf of clients. Search EnginesSearch engine optimization is available as a stand-alone service or as a part of a larger marketing campaign. Because SEO often requires making changes to the source code of a site, it is often most effective when incorporated into the initial development and design of a site, leading to the use of the term "Search Engine Friendly" to describe designs, menus, Content management systems and shopping carts that can be optimized easily and effectively. A range of strategies and techniques are employed in SEO, including changes to a site's code (referred to as "on page factors") and getting links from other sites (referred to as "off page factors"). These techniques include two broad categories: techniques that search engines recommend as part of good design, and those techniques that search engines do not approve of and attempt to minimize the effect of, referred to as spamdexing. Some industry commentators classify these methods, and the practitioners who utilize them, as either "white hat SEO", or "black hat SEO". Other SEOs reject the black and white hat dichotomy as an over-simplification. HistoryWebmasters and 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 site to the various engines which would run spiders, programs that "crawled" a page and stored the collected data in a database. By 1996, SEO related email spam was commonplace. The earliest known use of the phrase "search engine optimization" was a spam posted on Usenet on July 26, 1997. The process involves a search engine spider downloading a page and 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 and where these are located, as well as any weight for specific words, as well as any and all links the page contains, which are then placed into a scheduler for crawling at a later date. At first, search engines were supplied with information about pages by the webmasters themselves. 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 indexing pages based upon meta data was found to be less than reliable, mostly because webmasters abused meta tags by including keywords that had nothing to do with the content of their pages, to artificially increase page impressions for their Website and increase their Ad Revenue. Cost Per Impression was at the time the common means of monetizing content websites. Inaccurate, incomplete, and inconsistent meta data in meta tags caused pages to rank for irrelevant searches, and fail to rank for relevant searches. Search engines responded by developing more complex ranking algorithms, taking into account additional factors including: * Text within the title tag * Domain name * URL directories and file names * HTML tags: headings, emphasized (<em>) and strongly emphasized (<strong>) text * Term frequency, both in the document and globally, often misunderstood and mistakenly referred to as Keyword density * Keyword proximity * Keyword adjacency * Keyword sequence * Alt attributes for images * Text within NOFRAMES tags * Web content development * Sitemaps Today the only major search engine that says it considers meta keywords in its ranking algorithms is Yahoo, though most experts feel that even there the attention paid to meta keywords is minimal. Explicit facts about the effectives of meta keywords are, however, not readily known, because of the secrecy used during the ranking of algorithms by the search engines. One could therefore recommend the use of meta keywords in webpages and limit them to 20 keywords or less. For example, the source code of this page shows that Wikipedia uses meta keywords. The "description" tag is, however, claimed by most SEO-experts to be more important. One could therefore recommend the use of both meta tags in webpages. 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 extensively on factors that were still within the webmasters' exclusive control, search engines continued to suffer from abuse and ranking manipulation. In order to provide better results to their users, search engines had to adapt to ensure their SERPs showed the most relevant search results, rather than useless pages stuffed with numerous keywords by unscrupulous webmasters using a bait-and-switch lure to display unrelated web pages. This led to the rise of a new kind of search engine. More Sophisticated Ranking AlgorithmsGoogle brought a new concept to evaluating web pages. This concept, called PageRank, has been important to the Google algorithm from the start. PageRank is an algorithm that weights a page's importance based upon the incoming links. PageRank estimates the likelihood that a given page will be reached by a web user who randomly surfed the web, and followed links from one page to another. In effect, this means that some links are more valuable than others, as a higher PageRank page is more likely to be reached by the random surfer. The PageRank algorithm proved very effective, and Google began to be perceived as serving the most relevant search results. On the back of strong word of mouth from programmers, Google became a popular search engine. Off-page factors weighted more heavily than on-page factors as Google identifed the manipulation of off-page to be more difficult. Despite being difficult to game, webmasters had already developed link building tools and schemes to influence the Inktomi search engine, and these methods proved similarly applicable to gaining PageRank. Many sites focused on exchanging, buying, and selling links, often on a massive scale. Inktomi, an earlier search engine using similar off-page factors, had forced webmasters to develop link building tools and schemes to infuence searches; these same tools proved applicable to Google's PageRank system. Thus an online industry spawned focused on selling links designed to improve PageRank and link popularity. To drive human site visitors, links from higher PageRank pages sell for more money. A proxy for the PageRank metric is still displayed in the Google Toolbar, though the displayed value is rounded to the nearest integer, and the toolbar is believed to be updated less frequently than the value used internally by Google. In 2002 a Google spokesperson stated that PageRank is only one of more than 100 algorithms used in ranking pages, and that while the PageRank toolbar is interesting for users and webmasters, "the value to search engine optimization professionals is limited" because the value is only an approximation. Many experienced SEOs recommend ignoring the displayed PageRank. Google — and other search engines — have, over the years, developed a wider range of off-site factors they use in their algorithms. The Internet was reaching a vast population of non-technical users who were often unable to use advanced querying techniques to reach the information they were seeking and the sheer volume and complexity of the indexed data was vastly different from that of the early days. Combined with increases in processing power, search engines have begun to develop predictive, semantic, linguistic and heuristic algorithms. Around the same time as the work that led to Google, IBM had begun work on the Clever Project , and Jon Kleinberg was developing the HITS algorithm. As a search engine may use hundreds of factors in ranking the listings on its SERPs; the factors themselves and the weight each carries can change continually, and algorithms can differ widely, with a web page that ranks #1 in a particular search engine possibly ranking #200 in another search engine, or even on the same search engine a few days later. Google, Yahoo, Microsoft and Ask.com do not disclose the algorithms they use to rank pages. Some SEOs have carried out controlled experiments to gauge the effects of different approaches to search optimization. Based on these experiments, often shared through online forums and blogs, professional SEOs attempt to form a consensus on what methods work best, although consensus is rarely, if ever, actually reached. SEOs widely agree that the signals that influence a page's rankings include: 1. Keywords in the title tag. 2. Keywords in links pointing to the page. 3. Keywords appearing in visible text. 4. Link popularity. 5. (PageRank for Google) of the page. 6. Keywords in Heading Tag H1,H2 and H3 Tags in webpage. 7. Linking from one page to inner pages. 8. Placing punch line at the top of page. There are many other signals that may affect a page's ranking, indicated in a number of patents held by various search engines, such as historical data. More than Just Rankings Search engine optimization often involves more than just rankings. By improving the quality of a page's search listings, more users will select that page. Factors that may improve search listing quality include: an attention-grabbing title, an interesting description, and a domain and URL that reinforce the legitimacy of the site. Some commentators have noted that domains with lots of hyphens look spammy and may discourage click throughs. Relationship between SEO and search engines The first mentions of Search Engine Optimization do not appear on Usenet until 1997, a few years after the launch of the first Internet search engines. The operators of search engines recognized quickly that some people from the webmaster community were making efforts to rank well in their search engines, and even manipulating the page rankings in search results. In some early search engines, such as Infoseek, ranking first was as easy as grabbing the source code of the top-ranked page, placing it on your website, and submitting a URL to instantly index and rank that page. Due to the high value and targeting of search results, there is potential for an adversarial relationship between search engines and SEOs. In 2005, an annual conference named AirWeb was created to discuss bridging the gap and minimizing the sometimes damaging effects of aggressive web content providers. Some more aggressive site owners and SEOs generate automated sites or employ techniques that eventually get domains banned from the search engines. Many search engine optimization companies, which sell services, employ long-term, low-risk strategies, and most SEO firms that do employ high-risk strategies do so on their own affiliate, lead-generation, or content sites, instead of risking client websites. Some SEO companies employ aggressive techniques that get their client websites banned from the search results. The Wall Street Journal profiled a company that allegedly used high-risk techniques and failed to disclose those risks to its clients. Wired reported the same company sued a blogger for mentioning that they were banned. Google's Matt Cutts later confirmed that Google did in fact ban Traffic Power and some of its clients. Some search engines have also reached out to the SEO industry, and are frequent sponsors and guests at SEO conferences and seminars. In fact, with the advent of paid inclusion, some search engines now have a vested interest in the health of the optimization community. All of the main search engines provide information/guidelines to help with site optimization: Google's, Yahoo!'s, MSN's and Ask.com's. 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. Yahoo! has Site Explorer that provides a way to submit your URLs for free (like MSN/Google), determine how many pages are in the Yahoo! index and drill down on inlinks to deep pages. Yahoo! has an Ambassador Program and Google has a program for qualifying Google Advertising Professionals. Getting Into Search Engines' Databases
"White Hat" Methods
"Black Hat" Methods
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Search Engine Optimization 