Search engine optimization

From Wikipedia, the free encyclopedia.

Search engine optimization (SEO) is a set of methods aimed at improving the ranking of a website in search engine listings. The term also refers to an industry of consultants that carry out optimization projects on behalf of clients' sites.

Using search engines, visitors can find sites in a variety of ways: via paid-for advertisements in the search engine results pages (SERPs), via third parties who are listed in the search engines, or via "organic" listings, i.e. the results the search engines present users. SEO is primarily concerned with improving the visibility of a site in the organic search results.

High rankings in the organic search results can provide targeted traffic for a site. Obtaining that traffic by other means can potentially be expensive. For particularly competitive terms, the cost per click can run several dollars, or more, when pay per click advertising or banner advertising are used. For even moderately competitive terms the cost can range from a few cents to several tens of dollars per visitor. Given those costs, it often makes sense for site owners to optimize their sites for organic search.

Not all sites have identical goals in mind when they optimize for search engines. Some sites are seeking any and all traffic, and may be optimized to rank highly for common search phrase. This can be a poor marketing strategy for a business because it can generate a large volume of low-quality inquiries that cost money to handle, yet result in little business. The "shotgun approach" to search optimization can possibly work well for a site that has broad interest, such as a periodical, a directory, or site that displays advertising with a CPM revenue model.

Other sites target a specific population, with particular needs or interests. Many businesses try to optimize their sites for large numbers of highly specific keywords that indicate a prospective customer who is ready to buy their product. Focusing on desired traffic can generate more high-quality sales leads, and fewer time-wasting inquiries.

1 History
2 The relationship between SEOs and the search engines
3 Getting discovered by search engines
4 "Ethical" methods
5 "Unethical" methods
6 High Quality Web Sites Typically Rank Well
7 Related fields
8 See also
9 References
10 External links

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History

SEO began 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 to "crawl" the site, and store the collected data. The search engines then sorted the information by topic, and serve results based on pages they had spidered. As the number of documents online kept growing, and more webmasters realised the value of organic search listings, it became imperative for search engines to sort the vast collection of pages they had spidered and display the most relevant pages first. This was the start of a search engine vs. SEO struggle that continues to this day.

Initially, search engines were guided by the webmasters themselves. Early versions of search algorithms relied on webmaster-provided information like meta tags. Meta tags provided a guide to each page's content and relevant keywords. Soon some webmasters began to abuse meta tags, causing their pages to rank for irrelevant searches. In response, search engines developed more complex algorithms, taking into account a wider range of factors, but they still relied largely on what are today known as "on-site" factors. Examples of on-site factors include:

Keywords in the domain name
Keywords in the site's directory and file names
Page titles and tags: for example, a phrase marked up as an H1 (heading) element was considered to contain keywords relevant to the page
Ratio of the keyword(s) to other words on the page, the keyword density
Content of alternate text provided in the form of Alt tags for images, noframes text for browsers not able to display framed pages, etc.

The inherent flaw in relying so extensively on that factors was that webmasters and SEOs had full control over them and could "optimize" their pages for better rankings. Search engines had to adapt again to ensure their SERPs showed the most relevant pages rather than the best optimized ones.

A new search engine emerged with a new kind of thinking. Google was started by two PhD students at Stanford University, Sergey Brin and Larry Page, and brought a new concept to ranking web pages. This concept, called PageRank, was, for many years, the mainstay of the Google algorithm [1]. PageRank relied heavily on incoming links and used the logic that each link to a page is a vote for that page's value. The more incoming links a page had the more "worthy" it was. The value of each incoming link itself varied directly based on the PageRank of the page it was coming from and inversely on the number of outgoing links on that page. PageRank proved to be very good at serving relevant results. Google became the most popular and successful search engine. Because PageRank measured an off-site factor, it was more difficult to manipulate - at first.

But manipulated it was. Given time, and the realization that PageRank was the new game in town, webmasters focused on exchanging, buying, and selling links on a massive scale. PageRank's reliance on the link as a vote of confidence in a page's value was undermined as many webmasters sought to garner links purely to influence Google into sending them more traffic, irrespective of whether the link was useful to human site visitors.

It was time for Google—and other search engines—to look at a wider range of off-site factors. There were other reasons to develop more intelligent 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 to the early days. Search engines had to develop predictive, semantic, linguistic and heuristic algorithms.

The PageRank metric itself is still displayed in the Google Toolbar, but it is only one of several factors that Google considers in ranking pages.

Today, most search engines keep their methods and ranking algorithms secret. A search engine may use hundreds of factors in ranking the listings on its SERPs; the factors themselves and the weight each carries may change continually.

Much current SEO thinking on what works and what doesn't is largely speculation and informed guesses. Some SEOs have carried out controlled experiments to guage the effects of different approaches to search optimization.

The following, though, are some of the considerations search engines could be building into their algorithms, and the list of Google patents [2] may give some indication as to what is in the pipeline:

Age of site
Length of time domain has been registered
Age of content
Regularity with which new content is added
Age of link and reputation of linking site
Standard on-site factors
Negative scoring for on-site factors (for example, a dampening for sites with extensive keyword meta tags indicative of having being SEO-ed)
Uniqueness of content
Related terms used in content (the terms the search engine associates as being related to the main content of the page)
External links, the anchor text in those external links and in the sites/pages containing those links
Citations and research sources (indicating the content is of research quality)
Stem-related terms in the search engine's database (finance/financing)
Incoming backlinks and anchor text of incoming backlinks
Negative scoring for some incoming backlinks (perhaps those coming from low value pages, reciprocated backlinks, etc.)
Rate of acquisition of backlinks: too many too fast could indicate "unnatural" link buying activity
Text surrounding outward links and incoming backlinks. A link following the words "Sponsored Links" could be ignored
Use of "rel=nofollow" to suggest that the search engine should ignore the link
Depth of document in site
Metrics collected from other sources, such as monitoring how frequently users hit the back button when SERPs send them to a particular page
Metrics collected from sources like the Google Toolbar, Google AdWords/Adsense programs, etc.
Metrics collected in data-sharing arrangements with third parties (like providers of statistical programs used to monitor site traffic)
Rate of removal of incoming links to the site
Use of sub-domains, use of keywords in sub-domains and volume of content on sub-domains… and negative scoring for such activity
Semantic connections of hosted documents
Rate of document addition or change
IP of hosting service and the number/quality of other sites hosted on that IP
Other affiliations of linking site with the linked site (do they share an IP? have a common postal address on the "contact us" page?)
Technical matters like use of 301 to redirect moved pages, showing a 404 server header rather than a 200 server header for pages that don't exist, proper use of robots.txt
Hosting uptime
Whether the site serves different content to different categories of users (cloaking)
Broken outgoing links not rectified promptly
Unsafe or illegal content
Quality of HTML coding, presence of coding errors
Actual click through rates observed by the search engines for listings displayed on their SERPs
Hand ranking by humans of the most frequently accessed SERPs

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The relationship between SEOs and the search engines

In the early 2000, search engines and SEO firms attempted to establish an unofficial 'truce'. There are several tiers of SEO firms, and the more reputable companies employ content-based optimizations which meet with the search engines' (reluctant) approval. These techniques include improvements to site navigation and copywriting, designed to make websites more intelligible to search engine algorithms.

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, search engines now have a vested interest in the health of the optimization community.

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Getting discovered by search engines

New sites no longer need to be submitted to search engines to be listed. A simple link from an established site will get the search engines to visit the new site and spider its contents. It is rarely more than a few days from the acquisition of the link to all the main search engine spiders visiting and indexing the new site.

Naturally, this means that it is good practice to have some means (such as a site map, or plain hypertext links) so that once a spider finds part of a site, it can navigate to the rest. Otherwise, individual, isolated, dead-end pages must be found one-by-one from outside the site; any pages that are not linked to from outside can only be found by links internal to the site.

For those search engines, like Yahoo, who have their own paid submission, it may save some time to pay a nominal fee for submission.

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"Ethical" methods

So-called "Ethical" methods of SEO involve following the search engines' guidelines as to what is and what isn't acceptable. Their advice generally is to create content for the user, not the search engines; to make that content easily accessible to their spiders; and to not try to game their system. Often webmasters make critical mistakes when designing or setting up their web sites, and "poison" them so that they will not rank well. Ethical SEO attempts to discover and correct mistakes, such as machine-unreadable menus, broken links, temporary redirects, or a generally poor navigation structure that places pages too many clicks from the home page.

Because search engines are text-centric, many of the same methods that are useful for web accessibility are also advantageous for SEO. Methods are available for optimizing graphical content, even Flash animation (by placing a paragraph or division within, and at the end of the enclosing OBJECT tag), so that search engines can interpret the information.

Some methods considered ethical by the search engines:

Using a robots.txt file to grant permissions to spiders to access, or avoid, specific files and directories in the site
Using a short and relevant page title to name each page
Using a reasonably sized description meta tag without excessive use of keywords, exclamation marks or off topic comments
Keeping the page accessible via links from other pages on the site and, preferably, from a sitemap
Developing links via natural methods: Google doesn't elaborate on this somewhat vague guideline, but buying a link from an off-topic page purely because it has a high PageRank is probably not considered acceptable. Dropping an email to a fellow webmaster telling him about a great article you've just posted, and requesting a link, is most likely acceptable.

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"Unethical" methods

As search engines operate in a highly automated way it is often possible for webmasters to use methods and tactics not approved by search engines to gain better ranking. These methods often go unnoticed unless an employee from the search engine manually visits the site and notices the activity, or a change in ranking algorithm causes the site to lose the advantage thus gained. Sometimes a company will employ an SEO consultant to evaluate competitor's sites, and report "unethical" optimization methods to the search engines.

So-called "unethical" methods may include:

Keyword spamming (or keyword stuffing) involves the insertion of hidden, random text on a webpage to raise the keyword density or ratio of keywords to other words on the page. Hiding text out of view of the visitor's screen is done in many different ways. A popular technique is text colored to blend with the background. Using CSS "Z" positioning to place text "behind" an image -- and therefore out of view of the visitor -- is also common. Other ways include using CSS absolute positioning to have the text positioned several feet away from the page center and, again, out of physical view of the visitor but plainly text that any search engine would pick up in a crawl of the page. Invisible text is a bad idea, as of 2005, because top search engines apparently can detect it.

Abusing NOSCRIPT tags is another way to place hidden content within a page so that the search engines will index it, but the visitor won't see the content. NOSCRIPT tags are also a valid optimization method for displaying an alternative representation of JavaScript content, such as dynamic methods. The NOSCRIPT tags is not unethical by itself, only if misused.

The inserted text sometimes includes words that are frequently searched (such as "sex") even if those terms bear little connection to the content of the page. The goal in these cases is plainly to increase traffic at all costs whether that traffic is relevant or not. Once traffic comes to the page, the unethical webmaster may hope to monetize the traffic by displaying ads.

Spamdexing is the promotion of irrelevant, chiefly commercial, pages through abuse of the search algorithms. Many search engine administrators consider any form of search engine optimization used to improve a website's page rank as spamdexing. However, over time a widespread consensus has developed in the industry as to what are and are not acceptable means of boosting one's search engine placement and resultant traffic.

Cloaking refers to any of several means to serve up a different page to the search-engine spider than will be seen by human users. It can be an attempt to mislead search engines regarding the content on a particular web site. It should be noted, however, that cloaking can also be used to ethically increase accessibility of a site to users with disabilities, or to provide human users with content that search engines aren't able to process or parse. It is also used to deliver content based on a user's location; Google themselves use IP delivery, a form of cloaking, to deliver results.

Link spam is the placing or solicitation of links randomly on other sites, placing a desired keyword into the hyperlinked text of the inbound link. Guest books, forums, blogs and any site that accepts visitors comments are particular targets and are often victims of drive by spamming where automated software creates nonsense posts with links that are usually irrelevant and unwanted.

The following techniques are also widely acknowledged as being spam, or "black hat":

Some SEOs argue that the terms ethical and unethical should not be applied to the work they do. They maintain that on the principle of basic freedom everybody should be free to post whatever they choose on a site they own, as long as they stay within the law. The responsibility to block search engines access to that content is not one the webmaster should automatically assume. SEOs then explain that typically search engines visit sites uninvited and help themselves to the entire content of that site. Should the search engine then apply some software to "digest" that content and use it in their search results (often monetized with their own advertising) then pinning an "unethical" label on the webmaster is neither fair nor accurate. The flip side is that when a webmaster submits a site to a search engine he is actually inviting the search engine over. However, nowadays, the invitation is unnecessary as search engine spiders are aggressive in finding links to new pages and in crawling that new content, often within hours or minutes, unless they have specifically been excluded by a webmaster-prepared robots.txt file, or a robots exclusion meta tag.

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High Quality Web Sites Typically Rank Well

A webmaster who wants to maximize the value of a web site can read the guidelines published by the search engines, as well as the coding guidelines published by the World Wide Web Consortium. If the guidelines are followed, and the site presents frequently updates, useful, original content, and a few meaningful, useful inbound links are established, it is usually possible to obtain a significant amount of organic search traffic.

When a site has useful content, other webmasters will naturally place links to the site, increasing its PageRank and flow of visitors. When visitors discover a useful web site, they tend to refer other visitors by emailing or instant messaging links.

As a result, SEO practices that improve web site quality are likely to outlive short term practices that simply seek to manipulate search rankings. The top SEOs recommend targeting the same thing that search engines seek to promote: relevant, useful content for their users. Means of improving web site quality include:

Clean, standards-compliant websites that load quickly, are content rich, and frequently updated.
Websites that follow the web's simpler conventions (short and descriptive titles, easy navigation, no disabling of browser buttons, no keyword stuffing or other blatant SEO work).
Natural-looking link building: a few links from directories, very minimal reciprocal or three-way linking, no apparent buying or selling of links, no attempted PR manipulation (buying/selling/hogging), no outward links to less reputable sites.
No auto-generated nonsense content and no machine translated content, but original, useful material.
No technical errors, no duplicate pages, a valid robots.txt, a sitemap, and custom error pages.

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