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.[3]
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.
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, poor quality
or irrelevant search results could lead 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 penalize websites that used
manipulative techniques to improve their rankings on the search engine.
In September 2013, Google released the Google Hummingbird update, an algorithm change designed to improve Google's natural language processing and semantic understanding of web pages.
FROM:http://en.wikipedia.org/wiki/Search_engine_optimization#White_hat_versus_black_hat_techniques
