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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.[5] 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.[6]
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.[7] 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.[8] 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.[9]
By 2004, 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.[10] The leading search
engines, Google and Yahoo, do not disclose the algorithms
they use to rank pages. Notable SEO service providers,
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.[11][12] SEO practitioners
may also study patents held by various search engines
to gain insight into the algorithms.[13]
In 2005 Google
began personalizing search results for each user. Depending
on their history of previous searches, Google crafted
results for logged in users.[14] In 2008, Bruce Clay
said that "ranking is dead" because of personalized
search. It would become meaningless to discuss how a
website ranked, because its rank would potentially be
different for each user and each search.[15]
In 2007 Google
announced a campaign against paid links that transfer
PageRank.[16] 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.[17]
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. [18]
In December 2009
Google announced it would be using the web search history
of all its users in order to populate search results.[19]
Real-time-search
was introduced in late 2009 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.[20]
Contact
Email:
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