QUOTE(CaptainRon @ Jan 7 2006, 08:01 PM)
hi all
my page
http://iron-eagles.tripod.com/index.html had a page rank of 5 at one time. What i heard was google page rank is the number of other links linking to you. Now after a long time, around 2 years, I see that my page's rank had become 0!!
Now what exactly was the cause of this?
yes, also to mention that my page was unupdated too.
Google takes into consideration a lot of things to rank your page.
Quoting from the original Google paper, PageRank is defined like this:
We assume page A has pages T1...Tn which point to it (i.e., are citations). The parameter d is a damping factor which can be set between 0 and 1. We usually set d to 0.85. There are more details about d in the next section. Also C(A) is defined as the number of links going out of page A. The PageRank of a page A is given as follows:
PR(A) = (1-d) + d (PR(T1)/C(T1) + ... + PR(Tn)/C(Tn))
Note that the PageRanks form a probability distribution over web pages, so the sum of all web pages' PageRanks will be one.
PageRank or PR(A) can be calculated using a simple iterative algorithm, and corresponds to the principal eigenvector of the normalized link matrix of the web.
but that’s not too helpful so let’s break it down into sections.
PR(Tn) - Each page has a notion of its own self-importance. That’s “PR(T1)” for the first page in the web all the way up to “PR(Tn)” for the last page
C(Tn) - Each page spreads its vote out evenly amongst all of it’s outgoing links. The count, or number, of outgoing links for page 1 is “C(T1)”, “C(Tn)” for page n, and so on for all pages.
PR(Tn)/C(Tn) - so if our page (page A) has a backlink from page “n” the share of the vote page A will get is “PR(Tn)/C(Tn)”
d(... - All these fractions of votes are added together but, to stop the other pages having too much influence, this total vote is “damped down” by multiplying it by 0.85 (the factor “d”)
(1 - d) - The (1 – d) bit at the beginning is a bit of probability math magic so the “sum of all web pages' PageRanks will be one”: it adds in the bit lost by the d(.... It also means that if a page has no links to it (no backlinks) even then it will still get a small PR of 0.15 (i.e. 1 – 0.85). (Aside: the Google paper says “the sum of all pages” but they mean the “the normalised sum” – otherwise known as “the average” to you and me.
FinallyPageRank is, in fact, very simple (apart from one scary looking formula). But when a simple calculation is applied hundreds (or billions) of times over the results can seem complicated.
PageRank is also only part of the story about what results get displayed high up in a Google listing. For example there’s some evidence to suggest that Google is paying a lot of attention these days to the text in a link’s anchor when deciding the relevance of a target page – perhaps more so than the page’s PR…
PageRank is still part of the listings story though, so it’s worth your while as a good designer to make sure you understand it correctly.
LinksThe original PageRank paper by Google’s founders Sergey Brin and Lawrence Page -
http://www-db.stanford.edu/~backrub/google.html Chris Ridings’ “PageRank Explained” paper which, as of April 2002
http://web.archive.org/web/*/http://www.go...uk/PageRank.pdf , contains one major mistake/misunderstanding -
http://www.goodlookingcooking.co.uk/PageRank.pdf Phil Craven’s PageRank Calculator (fortunately his figures agree with mine)
A detailed explanation of how easy it is to alter the PageRank equation by mistake
An excellent discussion on chad-jams (including “pregnant chad”) by Douglas W. Jones -
http://www.cs.uiowa.edu/~jones/cards/chad.html - I don’t think many people know the United States’ voting system is this flawed!!!
Discussion forums on this topic:
MarketPositionTalk - PageRank updates
SearchEngineForums - PR documents and calculator
WebmasterWorld - PR document and calculator
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