From Wikipedia, the free encyclopedia
Search engine optimization (SEO) is the process of improving the volume and quality of traffic to a web site from search engines via "natural" ("organic" or "algorithmic") search results.
Usually, the earlier a site is presented in the search results, or the
higher it "ranks," the more searchers will visit that site. SEO can
also target different kinds of search, including image search, local search, and industry-specific vertical search engines.
As an Internet marketing
strategy, SEO considers how search engines work and what people search
for. Optimizing a website primarily involves editing its content and
HTML coding to both increase its relevance to specific keywords and to
remove barriers to the indexing activities
of search engines. Sometimes a site's structure (the relationships
between its content) must be altered too. Because of this it is, from a
client's perspective, always better to incorporate Search Engine
Optimization when a website is being developed than to try and
retroactively apply it.
The acronym "SEO" can also refer to "search engine optimizers," a term adopted by an industry of consultants
who carry out optimization projects on behalf of clients, and by
employees who perform SEO services in-house. Search engine optimizers
may offer SEO as a stand-alone service or as a part of a broader
marketing campaign. Because effective SEO may require changes to the HTML source code of a site, SEO tactics may be incorporated into web site development and design. The term "search engine friendly" may be used to describe web site designs, menus, content management systems and shopping carts that are easy to optimize.
Another class of techniques, known as black hat SEO or Spamdexing, use methods such as link farms and keyword stuffing
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.
[edit] History
Webmasters
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 page, or URL, to the various engines which would send a spider to "crawl" that page, extract links to other pages from it, and return information found on the page to be indexed.[1]
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.
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 earliest known use of the phrase search engine optimization was a spam message posted on Usenet on July 26, 1997.[2]
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, and inconsistent
data in meta tags caused pages to rank for irrelevant searches.[3]
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.[4]
By relying so much on factors exclusively within a webmaster's
control, early search engines suffered from abuse and 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 and 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.
While 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. The number calculated by the algorithm, PageRank, is a function of the quantity and strength of inbound links.[5]
PageRank estimates the likelihood that a given page will be reached by
a web user who randomly surfs the web, and 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 and Brin founded Google in 1998. Google attracted a loyal following among the growing number of Internet users, who liked its simple design.[6]
Off-page factors (such as PageRank and hyperlink analysis) were
considered as well as on-page factors (such as keyword frequency, meta tags,
headings, links and site structure) 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 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. Some of these schemes, or link farms, involved the creation of thousands of sites for the sole purpose of link spamming.[7] In recent years major search engines have begun to rely more heavily on off-web factors such as the age, sex, location, and search history of people conducting searches in order to further refine results.
By 2007, 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.[8] The three leading search engines, Google, Yahoo and Microsoft's Live Search, do not disclose the algorithms they use to rank pages. Notable SEOs, such as Rand Fishkin, Barry Schwartz, Aaron Wall and Jill Whalen, have studied different approaches to search engine optimization, and have published their opinions in online forums and blogs.[9][10] SEO practitioners may also study patents held by various search engines to gain insight into the algorithms.[11]
[edit] Webmasters and search engines
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.[12]
Due to the high marketing value of targeted search results, there is
potential for an adversarial relationship between search engines and
SEOs. In 2005, an annual conference, AIRWeb, Adversarial Information
Retrieval on the Web,[13] was created to discuss and 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 reported on a company, Traffic Power, which allegedly used high-risk techniques and failed to disclose those risks to its clients.[14] Wired magazine reported that the same company sued blogger Aaron Wall for writing about the ban.[15] Google's Matt Cutts later confirmed that Google did in fact ban Traffic Power and some of its clients.[16]
Some search engines have also reached out to the SEO industry, and
are frequent sponsors and guests at SEO conferences, chats, 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. Major search engines provide information and guidelines to
help with site optimization.[17][18][19] Google has a Sitemaps program[20]
to help webmasters learn if Google is having any problems indexing
their website and 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 and view link
information.[21]
[edit] Getting indexed
The leading search engines, Google, Yahoo! and 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.[22] Such programs usually guarantee inclusion in the database, but do not guarantee specific ranking within the search results.[23] Yahoo's paid inclusion program has drawn criticism from advertisers and competitors.[24] Two major directories, the Yahoo Directory and the Open Directory Project both require manual submission and human editorial review.[25] Google offers Google Webmaster Tools, for which an XML Sitemap
feed can be created and submitted for free to ensure that all pages are
found, especially pages that aren't discoverable by automatically
following links.[26]
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.[27]
[edit] Preventing indexing
-
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, and 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 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.[28]
[edit] White hat versus black hat
SEO techniques can be classified into two broad categories:
techniques that search engines recommend as part of good design, and
those techniques that search engines do not approve of. The search
engines attempt to minimize the effect of the latter, among them spamdexing. Industry commentators have classified these methods, and the practitioners who employ them, as either white hat SEO, or black hat SEO.[29]
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.[30]
An SEO technique is considered white hat if it conforms to the
search engines' guidelines and involves no deception. As the search
engine guidelines[31][17][18][19]
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 and 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, and 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,[32] 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 and Ricoh Germany for use of deceptive practices.[33] Both companies, however, quickly apologized, fixed the offending pages, and were restored to Google's list.[34]
[edit] As a marketing strategy
Eye tracking studies have shown that searchers scan a search results
page from top to bottom and 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.[35]
However, more search engine referrals does not guarantee more sales.
SEO is not necessarily an appropriate strategy for every website, and
other Internet marketing strategies can be much more effective,
depending on the site operator's goals.[36]
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 and other pages, building high quality web pages to
engage and persuade, addressing technical issues that may keep search
engines from crawling and indexing those sites, setting up analytics
programs to enable site owners to measure their successes, and
improving a site's conversion rate.[37]
SEO may generate a return on investment.
However, search engines are not paid for organic search traffic, their
algorithms change, and there are no guarantees of continued referrals.
Due to this lack of guarantees and certainty, a business that relies
heavily on search engine traffic can suffer major losses if the search
engines stop sending visitors.[38] It is considered wise business practice for website operators to liberate themselves from dependence on search engine traffic.[39] A top-ranked SEO blog Seomoz.org[40]
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.[41]
[edit] International markets
A Baidu search results page
The search engines' market shares vary from market to market, as does competition. In 2003, Danny Sullivan stated that Google represented about 75% of all searches.[42]
In markets outside the United States, Google's share is often larger,
and Google remains the dominant search engine worldwide as of 2007.[43] As of 2006, Google held about 40% of the market in the United States, but Google had an 85-90% market share in Germany.[44] While there were hundreds of SEO firms in the US at that time, there were only about five in Germany.[44]
In Russia the situation is reversed. Local search engine Yandex controls 50% of the paid advertising revenue, while Google has less than 9%.[45] In China, Baidu continues to lead in market share, although Google has been gaining share as of 2007.[46]
Successful search optimization for international markets may require professional translation of web pages, registration of a domain name with a top level domain in the target market, and web hosting that provides a local IP address. Otherwise, the fundamental elements of search optimization are essentially the same, regardless of language.[44]
[edit] Legal precedents
On October 17, 2002, SearchKing
filed suit in the United States District Court, Western District of
Oklahoma, against the search engine Google. SearchKing's claim was that
Google's tactics to prevent spamdexing
constituted a tortious interference with contractual relations. On May
27, 2003, the court granted Google's motion to dismiss the complaint
because SearchKing "failed to state a claim upon which relief may be
granted."[47][48]
In March 2006, KinderStart
filed a lawsuit against Google over search engine rankings.
Kinderstart's web site was removed from Google's index prior to the
lawsuit and the amount of traffic to the site dropped by 70%. On March
16, 2007 the United States District Court for the Northern District of California (San Jose Division) dismissed KinderStart's complaint without leave to amend, and partially granted Google's motion for Rule 11 sanctions against KinderStart's attorney, requiring him to pay part of Google's legal expenses. [49][50]
[edit] See also
[edit] References
- ^ Brian Pinkerton. "Finding What People Want: Experiences with the WebCrawler" (PDF). The Second International WWW Conference Chicago, USA, October 17–20, 1994. Retrieved on 2007-05-07.
- ^ Danny Sullivan (June 14, 2004). "Who Invented the Term "Search Engine Optimization"?". Search Engine Watch. Retrieved on 2007-05-14. See Google groups thread.
- ^ Cory Doctorow (August 26, 2001). "Metacrap: Putting the torch to seven straw-men of the meta-utopia". e-LearningGuru. Retrieved on 2007-05-08.
- ^ Pringle, G., Allison, L., and Dowe, D. (April 1998). "What is a tall poppy among web pages?". Proc. 7th Int. World Wide Web Conference. Retrieved on 2007-05-08.
- ^ Brin, Sergey and Page, Larry (1998). "The Anatomy of a Large-Scale Hypertextual Web Search Engine". Proceedings of the seventh international conference on World Wide Web. Retrieved on 2007-05-08.
- ^ Thompson, Bill (December 19, 2003). "Is Google good for you?". BBC News. Retrieved on 2007-05-16.
- ^ Zoltan Gyongyi and Hector Garcia-Molina (2005). "Link Spam Alliances" (PDF). Proceedings of the 31st VLDB Conference, Trondheim, Norway. Retrieved on 2007-05-08.
- ^ "Google Keeps Tweaking Its Search Engine". New York Times (June 3, 2007). Retrieved on 2007-06-06.
- ^ Danny Sullivan (September 29, 2005). "Rundown On Search Ranking Factors". Search Engine Watch. Retrieved on 2007-05-08.
- ^ "Search Engine Ranking Factors V2". SEOmoz.org (April 2, 2007). Retrieved on 2007-05-14.
- ^ Christine Churchill (November 23, 2005). "Understanding Search Engine Patents". Search Engine Watch. Retrieved on 2007-05-08.
- ^ Laurie J. Flynn (November 11, 1996). "Desperately Seeking Surfers". New York Times. Retrieved on 2007-05-09.
- ^ "AIRWeb". Adversarial Information Retrieval on the Web, annual conference. Retrieved on 2007-05-09.
- ^ David Kesmodel (September 22, 2005). "Sites Get Dropped by Search Engines After Trying to 'Optimize' Rankings". Wall Street Journal. Retrieved on 2008-07-30.
- ^ Adam L. Penenberg (September 8, 2005). "Legal Showdown in Search Fracas". Wired Magazine. Retrieved on 2007-05-09.
- ^ Matt Cutts (February 2, 2006). "Confirming a penalty". mattcutts.com/blog. Retrieved on 2007-05-09.
- ^ a b "Google's Guidelines on Site Design". google.com. Retrieved on 2007-04-18.
- ^ a b "Site Owner Help: MSN Search Web Crawler and Site Indexing". msn.com. Retrieved on 2007-04-18.
- ^ a b "Yahoo! Search Content Quality Guidelines". help.yahoo.com. Retrieved on 2007-04-18.
- ^ "Google Webmaster Tools". google.com. Retrieved on 2007-05-09.
- ^ "Yahoo! Site Explorer". yahoo.com. Retrieved on 2007-05-09.
- ^ "Submitting To Search Crawlers: Google, Yahoo, Ask & Microsoft's Live Search". Search Engine Watch (2007-03-12). Retrieved on 2007-05-15.
- ^ "Search Submit". searchmarketing.yahoo.com. Retrieved on 2007-05-09.
- ^ "Questionable Results at Revamped Yahoo". Washington Post (2004-03-11). Retrieved on 2007-05-23.
- ^ "Submitting To Directories: Yahoo & The Open Directory". Search Engine Watch (2007-03-12). Retrieved on 2007-05-15.
- ^ "What is a Sitemap file and why should I have one?". google.com. Retrieved on 2007-03-19.
- ^ Cho, J., Garcia-Molina, H. (1998). "Efficient crawling through URL ordering". Proceedings of the seventh conference on World Wide Web, Brisbane, Australia. Retrieved on 2007-05-09.
- ^ "Newspapers Amok! New York Times Spamming Google? LA Times Hijacking Cars.com?". Search Engine Land (May 8, 2007). Retrieved on 2007-05-09.
- ^ Andrew Goodman. "Search Engine Showdown: Black hats vs. White hats at SES". SearchEngineWatch. Retrieved on 2007-05-09.
- ^ Jill Whalen (November 16, 2004). "Black Hat/White Hat Search Engine Optimization". searchengineguide.com. Retrieved on 2007-05-09.
- ^ "What's an SEO? Does Google recommend working with companies that offer to make my site Google-friendly?". google.com. Retrieved on 2007-04-18.
- ^ Andy Hagans (November 8, 2005). "High Accessibility Is Effective Search Engine Optimization". A List Apart. Retrieved on 2007-05-09.
- ^ Matt Cutts (February 4, 2006). "Ramping up on international webspam". mattcutts.com/blog. Retrieved on 2007-05-09.
- ^ Matt Cutts (February 7, 2006). "Recent reinclusions". mattcutts.com/blog. Retrieved on 2007-05-09.
- ^ "A New F-Word for Google Search Results". Search Engine Watch (March 8, 2005). Retrieved on 2007-05-16.
- ^ "What SEO Isn't". blog.v7n.com (June 24, 2006). Retrieved on 2007-05-16.
- ^ Melissa Burdon (March 13, 2007). "The Battle Between Search Engine Optimization and Conversion: Who Wins?". Grok.com. Retrieved on 2007-05-09.
- ^ Andy Greenberg (April 30, 2007). "Condemned To Google Hell". Forbes. Retrieved on 2007-05-09.
- ^ Jakob Nielsen (January 9, 2006). "Search Engines as Leeches on the Web". useit.com. Retrieved on 2007-05-14.
- ^ "SEOmoz: Best SEO Blog of 2006". searchenginejournal.com (January 3, 2007). Retrieved on 2007-05-31.
- ^ "A survey of 25 blogs in the search space comparing external metrics to visitor tracking data". seomoz.org. Retrieved on 2007-05-31.
- ^ "The search engine that could", USA Today (2003-08-26). Retrieved on 2007-05-15.
- ^ "Stats Show Google Dominates the International Search Landscape". Search Engine Watch (2007-02-22). Retrieved on 2007-05-15.
- ^ a b c Mike Grehan (April 3, 2006). "Search Engine Optimizing for Europe". Click. Retrieved on 2007-05-14.
- ^ Pfanner, Eric (December 18, 2006). "New to Russia, Google Struggles to Find Its Footing", New York Times. Retrieved on 2007-05-15.
- ^ "Google Gaining, But Baidu Still Dominates In China". Search Engine Land (March 6, 2007). Retrieved on 2007-05-15.
- ^ "Search King, Inc. v. Google Technology, Inc., CIV-02-1457-M" (PDF). docstoc.com (May 27, 2003). Retrieved on 2008-05-23.
- ^ Stefanie Olsen (May 30, 2003). "Judge dismisses suit against Google". CNET. Retrieved on 2007-05-10.
- ^ "Technology & Marketing Law Blog: KinderStart v. Google Dismissed—With Sanctions Against KinderStart's Counsel". blog.ericgoldman.org. Retrieved on 2008-06-23.
- ^ "Technology & Marketing Law Blog: Google Sued Over Rankings—KinderStart.com v. Google". blog.ericgoldman.org. Retrieved on 2008-06-23.
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