Search engine optimization (SEO)
Search
engine optimization (SEO) is the process of affecting the
visibility of a website or a web page in a search engine's "natural"
or un-paid ("organic") search results.jargon] In general,
the earlier (or higher ranked on the search results page), and more
frequently a site appears in the search results list, the more
visitors it will receive from the search engine's users. SEO may
target different kinds of search, including image search, local
search, video search, academic search, news search and
industry-specific vertical search engines.
As an Internet marketing
strategy, SEO considers how search engines work, what people search
for, the actual search terms or keywords typed into search engines
and which search engines are preferred by their targeted audience.
Optimizing a website may involve editing its content, HTML and
associated coding to both increase its relevance to specific keywords
and to remove barriers to the indexing activities of search engines.
Promoting a site to increase the number of backlinks, or inbound
links, is another SEO tactic.
The plural of the
abbreviation SEO can refer to "search engine optimizers,"
those who provide SEO service.
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 webmasters needed to do was to submit the address
of 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.
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, and all links the page contains, which are then placed into a scheduler for crawling at a later date.
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, 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 phrase "search engine
optimization" probably came into use in 1997. The first
documented use of the term Search Engine Optimization was John
Audette and his company Multimedia Marketing Group as documented by a
web page from the MMG site from August, 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. Using
meta data to index pages was found to be less than reliable, however,
because the webmaster's choice of keywords in the meta tag could
potentially be an inaccurate representation of the site's actual
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.
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 such as keyword density which were
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.
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. 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.
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 gaming 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.
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 gaming 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.
By 2004, search engines had
incorporated a wide range of undisclosed factors in their ranking
algorithms to reduce the impact of link manipulation. In June 2007,
The New York Times' Saul Hansell stated Google ranks sites using more
than 200 different signals.
The leading search engines, Google, Bing, and Yahoo, do not disclose the algorithms they use to rank pages. Some SEO practitioners have studied different approaches to search engine optimization, and have shared their personal opinions
Patents related to search engines can provide information to better understand search engines.
The leading search engines, Google, Bing, and Yahoo, do not disclose the algorithms they use to rank pages. Some SEO practitioners have studied different approaches to search engine optimization, and have shared their personal opinions
Patents related to search engines can provide information to better understand search engines.
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. He opined that it would become meaningless to discuss how a website ranked, because its rank would potentially be different for each user and each search.
In 2008, Bruce Clay said that "ranking is dead" because of personalized search. He opined that it would become meaningless to discuss how a website ranked, because its rank would potentially be different for each user and each search.
In 2007, Google announced a
campaign against paid links that transfer PageRank.
On June 15, 2009, Google disclosed that they had taken measures to mitigate the effects of PageRank sculpting by use of the nofollow attribute on links. Matt Cutts, a well-known software engineer at Google, announced that Google Bot would no longer treat nofollowed links in the same way, in order to prevent SEO service providers from using nofollow for PageRank sculpting.
As a result of this change the usage of nofollow leads to evaporation of pagerank. In order to avoid the above, SEO engineers developed alternative techniques that replace nofollowed tags with obfuscated Javascript and thus permit PageRank sculpting. Additionally several solutions have been suggested that include the usage of iframes, Flash and Javascript.
On June 15, 2009, Google disclosed that they had taken measures to mitigate the effects of PageRank sculpting by use of the nofollow attribute on links. Matt Cutts, a well-known software engineer at Google, announced that Google Bot would no longer treat nofollowed links in the same way, in order to prevent SEO service providers from using nofollow for PageRank sculpting.
As a result of this change the usage of nofollow leads to evaporation of pagerank. In order to avoid the above, SEO engineers developed alternative techniques that replace nofollowed tags with obfuscated Javascript and thus permit PageRank sculpting. Additionally several solutions have been suggested that include the usage of iframes, Flash and Javascript.
In
December 2009, Google announced it would be using the web search
history of all its users in order to populate search results.
Google
Instant, real-time-search, was introduced in late 2010 in an attempt
to make search results more timely and relevant. Historically site
administrators have spent months or even years optimizing a website
to increase search rankings. With the growth in popularity of social
media sites and blogs the leading engines made changes to their
algorithms to allow fresh content to rank quickly within the search
results.
In
February 2011, Google announced the "Panda update, which
penalizes websites containing content duplicated from other websites
and sources. Historically websites have copied content from one
another and benefited in search engine rankings by engaging in this
practice, however Google implemented a new system which punishes
sites whose content is not unique.
In
April 2012, Google launched the Google Penguin update the goal of
which was to penalise websites that used manipulative techniques to
improve their rankings on the search engine.
Relationship with search engines
Yahoo and Google offices
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
Altavista and Infoseek, adjusted their algorithms in an effort to
prevent webmasters from manipulating rankings.
In
2005, an annual conference, AIRWeb, Adversarial Information Retrieval
on the Web was created to bring together practitioners and
researchers concerned with search engine optimisation and related
topics.
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.
Wired magazine reported that the same company sued blogger and SEO Aaron Wall for writing about the ban.
Google's Matt Cutts later confirmed that Google did in fact ban Traffic Power and some of its clients.
Wired magazine reported that the same company sued blogger and SEO Aaron Wall for writing about the ban.
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, 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.
Bing Toolbox provides a way from webmasters to submit a sitemap and web feeds, allowing users to determine the crawl rate, and how many pages have been indexed by their search engine
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.
Bing Toolbox provides a way from webmasters to submit a sitemap and web feeds, allowing users to determine the crawl rate, and how many pages have been indexed by their search engine
Getting indexed
The leading search engines, such
as Google, Bing 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. 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.
Two major directories, the Yahoo Directory and the Open Directory Project both require manual submission and human editorial review.
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 are not discoverable by automatically following links.
Such programs usually guarantee inclusion in the database, but do not guarantee specific ranking within the search results.
Two major directories, the Yahoo Directory and the Open Directory Project both require manual submission and human editorial review.
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 are not 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.
Suppose
each circle is a website, and an arrow is a link from one website to
another, such that a user can click on a link within, say, website F
to go to website B, but not vice versa. Search engines begin by
assuming that each website has an equal chance of being chosen by a
user. Next, crawlers examine which websites link to which other
websites and guess that websites with more incoming links contain
valuable information that users want.
Preventing crawling
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, 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.
Increasing prominence
A variety of methods can
increase the prominence of a webpage within the search results. 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.
Updating content so as to keep search engines crawling back frequently can give additional weight to a site. 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. URL normalization of web pages accessible via multiple urls, using the canonical link element
or via 301 redirects can help make sure links to different versions of the url all count towards the page's link popularity score.
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.
Updating content so as to keep search engines crawling back frequently can give additional weight to a site. 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. URL normalization of web pages accessible via multiple urls, using the canonical link element
or via 301 redirects can help make sure links to different versions of the url all count towards the page's link popularity score.
White hat versus black hat techniques
SEO
techniques can be classified into two broad categories: techniques
that search engines recommend as part of good design, and those
techniques of which search engines do not approve. 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.
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.
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 and
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 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 accessibilityalthough
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 example was the February 2006 Google removal of both BMW
Germany and Ricoh Germany for use of deceptive practices.
Both companies, however, quickly apologized, fixed the offending pages, and were restored to Google's list.
Both companies, however, quickly apologized, fixed the offending pages, and were restored to Google's list.
Technical details
Main article: Search engine
optimization
Crawlers
rely upon keyword placement within the text of an article, and
typically disregard images.
Text appearing in several key locations (such as the <title> and <meta> tags of the page's code) gets special attention because search engines compare information found there with other pages to determine relevance. SEO copywriters also strive for unique written content on the page, distinguishing it from similar pages competing for placement in the search results. Other factors that determine relevance during a search are the page's keyword density, the placement of the keywords, and the number of links to and from the page from other pages.
Text appearing in several key locations (such as the <title> and <meta> tags of the page's code) gets special attention because search engines compare information found there with other pages to determine relevance. SEO copywriters also strive for unique written content on the page, distinguishing it from similar pages competing for placement in the search results. Other factors that determine relevance during a search are the page's keyword density, the placement of the keywords, and the number of links to and from the page from other pages.
Professional role
SEO copywriting is most often
one of the various jobs of a copywriter. However, there are freelance
copywriters who hire out their services solely for SEO, agencies and
firms that specialize in SEO (including SEO copywriting), and
copywriting agencies that offer SEO copywriting as part of
comprehensive writing and editing services.
A freelance SEO copywriter
will work with a client to determine the appropriate keywords needed
to promote the client's business. Online keyword research tools are
then used to gather a list of potential phrases.
While an obvious goal of SEO
copywriting is to cause the business's or product's web page to rank
highly in a search, most experts in the field would argue that it is
of secondary priority. The foremost goal of SEO copywriting is to
produce succinct, effectively persuasive text for a well-written web
page that will motivate the reader to take action. Writing that
"optimizes" a search but offers little useful information
or only weak persuasion is frowned upon in the profession as
ineffective. At its worst, it becomes a costly resource inducing
potential buyers to turn away from the site rather than generating
sales. The main goal of the SEO copywriter remains writing
interesting content that people want to read and link to.
SEO copywriters often work
with "optimizers" who are more expert in the technical
aspects of SEO. Together they will not only rewrite text but also
alter the code to design a page that is most favored by search
engines. It is not a clear, scientific process, however. Attempting
to keep themselves competitive and defending against the composition
strategies of so-called black hat SEOs, search engine designers today
do not disclose the complex algorithmic processes of their search
engines. In spite of the insights of optimizing technicians, SEO
copywriting requires finesse and repeated experimentation to assess
how the team's page revisions will fare in a potential customer's
search.
As a marketing strategy
SEO
is not an appropriate strategy for every website, and other Internet
marketing strategies can be more effective, depending on the site
operator's goals.
A successful Internet marketing campaign may also depend upon building high quality web pages to engage and persuade, setting up analytics programs to enable site owners to measure results, and improving a site's conversion rate.
A successful Internet marketing campaign may also depend upon building high quality web pages to engage and persuade, setting up analytics programs to enable site owners to measure results, and improving a site's conversion rate.
SEO may generate an adequate
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.
Search engines can change their algorithms, impacting a website's placement, possibly resulting in a serious loss of traffic. According to Google's CEO, Eric Schmidt, in 2010, Google made over 500 algorithm changes – almost 1.5 per day.It is considered wise business practice for website operators to liberate themselves from dependence on search engine traffic.
Search engines can change their algorithms, impacting a website's placement, possibly resulting in a serious loss of traffic. According to Google's CEO, Eric Schmidt, in 2010, Google made over 500 algorithm changes – almost 1.5 per day.It is considered wise business practice for website operators to liberate themselves from dependence on search engine traffic.
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
competition. In 2003, Danny Sullivan stated that Google represented
about 75% of all searches.
In markets outside the United States, Google's share is often larger, and Google remains the dominant search engine worldwide as of 2007.
As of 2006, Google had an 85–90% market share in Germany.
While there were hundreds of SEO firms in the US at that time, there were only about five in Germany.
As of June 2008, the marketshare of Google in the UK was close to 90% according to Hitwise.
That market share is achieved in a number of countries.
In markets outside the United States, Google's share is often larger, and Google remains the dominant search engine worldwide as of 2007.
As of 2006, Google had an 85–90% market share in Germany.
While there were hundreds of SEO firms in the US at that time, there were only about five in Germany.
As of June 2008, the marketshare of Google in the UK was close to 90% according to Hitwise.
That market share is achieved in a number of countries.
As of 2009, there are only a
few large markets where Google is not the leading search engine. In
most cases, when Google is not leading in a given market, it is
lagging behind a local player. The most notable markets where this is
the case are China, Japan, South Korea, Russia and the Czech Republic
where respectively Baidu, Yahoo! Japan, Naver, Yandex and Seznam are
market leaders.
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.
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