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.
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.dubious – discuss] 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. 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.[10] 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 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.
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.
петък, 18 януари 2013 г.
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