A good Content of a site,Back links of A site and the popularity of the site..

Description

Google describes PageRank:

“ PageRank relies on the uniquely democratic nature of the web by using
its vast link structure as an indicator of an individual page's value. In
essence, Google interprets a link from page A to page B as a vote, by page
A, for page B. But, Google looks at more than the sheer volume of votes,
or links a page receives; it also analyzes the page that casts the vote.
Votes cast by pages that are themselves "important" weigh more heavily
and help to make other pages "important". ”


In other words, a PageRank results from a "ballot" among all the other
pages on the World Wide Web about how important a page is. A hyperlink
to a page counts as a vote of support. The PageRank of a page is defined
recursively and depends on the number and PageRank metric of all pages
that link to it ("incoming links"). A page that is linked to by many pages
with high PageRank receives a high rank itself. If there are no links to a
web page there is no support for that page.

Google assigns a numeric weighting from 0-10 for each webpage on the
Internet; this PageRank denotes a site’s importance in the eyes of Google.
The PageRank is derived from a theoretical probability value on a
logarithmic scale like the Richter Scale. The PageRank of a particular page
is roughly based upon the quantity of inbound links as well as the PageRank
of the pages providing the links. It is known that other factors, e.g.
relevance of search words on the page and actual visits to the page
reported by the Google toolbar also influence the PageRank. In order to
prevent manipulation, spoofing and spamdexing, Google provides no
specific details about how other factors influence PageRank.

Numerous academic papers concerning PageRank have been published
since Page and Brin's original paper. In practice, the PageRank concept has
proven to be vulnerable to manipulation, and extensive research has been
devoted to identifying falsely inflated PageRank and ways to ignore links
from documents with falsely inflated PageRank.

Other link-based ranking algorithms for Web pages include the HITS
algorithm invented by Jon Kleinberg (used by Teoma and now Ask.com
Search Engine - Better Web Search), the IBM CLEVER project, and the
TrustRank algorithm.

it is based on the Back links and the popularity of your site....

page rank is probably to most important software developed.This system, where the search engine uses the hyper linked structure on web pages to determine how important a web page or site is.

PageRank is Google’s scoring mechanism for determining a site’s importance by link popularity.

Originally Posted by arora

Page rank is as follows:
where p1,p2,...,pN are the pages under consideration, M(pi) is the set of pages that link to pi, L(pj) is the number of outbound links on page pj, and N is the total number of pages.

nice post sir.....

I think its hard to compute the PR of the site :P

Page rank also describes the authority of the particular page...

Does pr affect search result ranking or index rates?

well... Page Rank is the remark which shows how popular is your site amongst all sites. The same as you get in your school.