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 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. SEO can also target different kinds of search, including
image search, local search, and industry-specific vertical search
engines.
As a marketing strategy for increasing a site's relevance, SEO
considers how search algorithms work and what people search for.
SEO efforts may involve a site's coding, presentation, and 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, and making the site
more appealing to users. Another class of techniques, known as
black hat SEO or spamdexing, use methods such as link farms and
keyword stuffing that tend to harm search engine user experience.
Search engines look for sites that employ these techniques and
may remove them from their indexes.
The initialism "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.
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 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. 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.
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.
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. 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.[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, 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.
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 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. SEO practitioners may also study patents held by various
search engines to gain insight into the algorithms.
Webmasters and search engines
By 1997 search engines recognized that some webmasters were making
efforts to rank well in their search engines, and 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
and SEOs. In 2005, an annual conference, AIRWeb, Adversarial Information
Retrieval on the Web, 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 profiled a company, Traffic Power, that
allegedly used high-risk techniques and 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
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.
Major search engines provide information and guidelines to help
with site optimization. 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.
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. 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
and competitors. 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
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.
Preventing indexing
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.
White hat versus black hat
SEO techniques are classified by some into 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 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 permanantly 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 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 and Ricoh Germany for use of deceptive practices.
Both companies, however, quickly apologized, fixed the offending
pages, and were restored to Google's list.
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. 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. A successful Internet marketing campaign
may drive organic search results to 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.
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. 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.
International markets
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 held about 40% of the market in the United
States, but 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.
In Russia the situation is reversed. Local search engine Yandex
controls 50% of the paid advertising revenue, while Google has
less than 9%. In China, Baidu continues to lead in market share,
although Google has been gaining share as of 2007.
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.
Legal precedents
In 2002, SearchKing filed suit in an Oklahoma court against the
search engine Google. SearchKing's claim was that Google's tactics
to prevent spamdexing constituted an unfair business practice.
In May 2003, the court pronounced a summary judgment in Google's
favor.
In March 2006, KinderStart.com, LLC filed a First Amendment complaint
against Google and also attempted to include potential members
of the class of plaintiffs in a class action.[48] The plaintiff's
web site was removed from Google's index prior to the lawsuit
and the amount of traffic to the site plummeted. On March 16,
2007 the United States District Court 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.
See also
* Exclusion standards: robots exclusion standard (robots.txt),
meta elements, nofollow (link attribute)
* Related marketing topics: internet marketing, affiliate marketing,
email marketing, display advertising, web analytics
* Search marketing related topics: search engine marketing, social
media optimization, paid inclusion, pay per click (PPC), Google
bomb
* Search engine spam: spamdexing, web scraping, scraper site,
link farm, Free For All link page
* Wikipedia pages: FAQs for Businesses, Wikipedia:Search engine
optimization, Evaluating internet sources
* Linking: link popularity, link farm, nofollow, link exchange,
reciprocal link, multiway linking, link exchange network, backlink
* Other: landing page, IP delivery, Landing page optimization,
Human search engine, Stop words, Poison words
Major search engines
* Google
* Yahoo!
* Live Search by Microsoft, formerly MSN
* Ask.com, formerly Ask Jeeves
SEO organizations
* Search Engine Marketing Professional Organization
Notable SEOs
* Category:Search engine optimization consultants
Search engine representatives
* Dan Crow, Google
* Matt Cutts, Google
* Adam Lasnik, Google
* Jeremy Zawodny, Yahoo!
* Gary Price, Ask