PageRank is a link analysis
algorithm that assigns a numerical weighting to each element
of a hyperlinked set of documents, such as the World Wide
Web, with the purpose of "measuring" its relative importance
within the set. The algorithm may be applied to any
collection of entities with reciprocal quotations and
references. The numerical weight that it assigns to any
given element E is also called the PageRank of E and denoted
by PR(E).
PageRank was developed at Stanford University by Larry Page
(hence the name Page-Rank) and later Sergey Brin as part of
a research project about a new kind of search engine. The
project started in 1995 and led to a functional prototype,
named Google, in 1998. Shortly after, Page and Brin founded
Google Inc., the company behind the Google search engine.
While just one of many factors which determine the ranking
of Google search results, PageRank continues to provide the
basis for all of Google's web search tools.
The name PageRank is a trademark of Google. The PageRank
process has been patented (U.S. Patent 6,285,999 ). The
patent is not assigned to Google but to Stanford University.
Mathematical
PageRanks (out of 100) for a simple network (PageRanks
reported by google are rescaled logarithmically). Page C has
a higher PageRank than Page E, even though it has fewer
links to it: the link it has is much higher valued. A web
surfer who chooses a random link on every page (but with 15%
likelihood jumps to a random page on the whole web) is going
to be on Page E for 8.1% of the time. (The 15% likelihood of
jumping to an arbitrary page corresponds to a damping factor
of 85%.) Without damping, all web surfers would eventually
end up on Pages A, B, or C, and all other pages would have
PageRank zero. Page A is assumed to link to all pages in the
web, because it has no outgoing links.
Google directory PageRank
The Google Directory PageRank is an 8-unit measurement.
These values can be viewed in the Google Directory. Unlike
the Google Toolbar which shows the PageRank value by a
mouseover of the greenbar, the Google Directory does not
show the PageRank as a numeric value but only as a green
bar.
False or spoofed PageRank
While the PR
shown in the Toolbar is considered to be derived from an
accurate PageRank value (at some time prior to the time of
publication by Google) for most sites, it must be noted that
this value is also easily manipulated. A current flaw is
that any low PageRank page that is redirected, via a 302
server header or a "Refresh" meta tag, to a high PR page
causes the lower PR page to acquire the PR of the
destination page. In theory a new, PR0 page with no incoming
links can be redirected to the Google home page - which is a
PR 10 - and by the next PageRank update the PR of the new
page will be upgraded to a PR10. This spoofing technique,
also known as 302 Google Jacking, is a known failing or bug
in the system. Any page's PR can be spoofed to a higher or
lower number of the webmaster's choice and only Google has
access to the real PR of the page. Spoofing is generally
detected by running a Google search for a URL with
questionable PR, as the results will display the URL of an
entirely different site (the one redirected to) in its
results.
Manipulating PageRank
For search-engine
optimization purposes, some companies offer to sell high
PageRank links to webmasters. As links from higher-PR pages
are believed to be more valuable, they tend to be more
expensive. It can be an effective and viable marketing
strategy to buy link advertisements on content pages of
quality and relevant sites to drive traffic and increase a
webmaster's link popularity. However, Google has publicly
warned webmasters that if they are or were discovered to be
selling links for the purpose of conferring PageRank and
reputation, their links will be devalued (ignored in the
calculation of other pages' PageRanks). The practice of
buying and selling links is intensely debated across the
Webmastering community. Google advises webmasters to use the
nofollow HTML attribute value on sponsored links. According
to Matt Cutts, Google is concerned about webmasters who try
to game the system, and thereby reduce the quality of Google
search results.
Other Ways to Increase Trafics.