Introduction

- PageRank is a numeric value that represents how important a page is on the web.

- Old Algorithms considered only the content of the page causing web spamming .

- Google PageRank considers both content and anchor text(Back Links)

What is PageRank?

- PageRank is a “vote”, by all the other pages on the Web, about how important a page is.

- Determines a page’s ranking in the search results.

- The name PageRank is a trademark of Google which is patented to Stanford University.

- Quoting from the original Google paper, PageRank is defined like this:

“ 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". ”

Calculation of Page Rank

- Two Methods-Simplified Algorithm and Damping Algorithm

Simplified Algorithm:-

- In the general case, the Page Rank value for any page u can be expressed as:

Damping Algorithm:-

We assume page ’p’ has a set of pages pa[p] which point to it (i.e., are citations). The parameter d is a damping factor which can be set between 0and 1. We usually set d to 0.85. Also hq is defined as the number of links going out of page p. The PageRank xp of a page p is given as follows:

Xp = d qεpa[p] xq/hq + (1-d)

PageRank is calculated using Simple Iterative Method

Example

Each page has one outgoing link (the outgoing count is 1, i.e. hA = 1 and hB = 1).

Guess 1

We don’t know what their PR should be to begin with, so let’s take a guess at 1.0 and do some calculations:

d = 0.85

PR(A) = (1 – d) + d(PR(B)/1)

PR(B) = (1 – d) + d(PR(A)/1)

i.e. PR(A) = 0.15 + 0.85 * 1 = 1

PR(B) = 0.15 + 0.85 * 1 = 1

Here the numbers aren’t changing at all! So here we consider this as a good guess.

Guess 2

No, that’s too easy, maybe I got it wrong (and it wouldn’t be the first time). Ok, let’s start the guess at 0 instead and re-calculate:

PR(A) = 0.15 + 0.85 * 0 = 0.15

PR(B) = 0.15 + 0.85 * 0.15= 0.2775

And again:

PR(A) = 0.15 + 0.85 * 0.2775= 0.385875

PR(B) = 0.15 + 0.85 * 0.385875 = 0.47799375

and so on.

On 39th iteration we will get as PR(A)=.999999 and PR(B)=1.0000000 and finally at the 40th iteration we

will get PR(a)=1.000 and PR(B)=1.000.

And average pagerank =1.00000

Principle: it doesn’t matter where you start your guess, once the PageRank calculations have settled down, the “normalized probability distribution” (the average PageRank for all pages) will be 1.0.

Variations

Google Toolbar Rank

- The Google Toolbar's PageRank feature displays a visited page's PageRank as a whole number between 0 and 10.

SERP Rank

- The actual result returned by a search engine in response to a keyword query.

Google directory PageRank

- The Google Directory PageRank is an 8-unit measurement, shows PageRank as a green bar.

False or Spoofed PageRank

- Any low PageRank page that was redirected, via a 302 server header or a "Refresh" meta tag, to a high PageRank page caused the lower PageRank page to acquire the PageRank of the destination page.

- 302 Google Jacking

Manipulating PageRank

- For search-engine optimization purposes, some companies offer to sell high PageRank links to webmasters.

- Link Exchange

Optimization of PageRank

There are three fundamental areas to look at when trying to optimize the PageRank for site:

1. The links you choose to have link to you, i.e., which ones you choose, and how much effort you put in to getting them.

2. Who you choose to link out to from your site, and from which page of your site you place their link. (Maximising PageRank Feedback and minimising PageRank leakage).

3. The internal navigational structure and linkage of your pages, in order to best distribute PageRank within your site.

Removal of Dangling Pages

Dangling links are simply links that point to any page with no outgoing links.

It will affect the PageRank calculation because it is not clear where their weight should be distributed.

Need to be removed

Google’s rel=“nofollow” option

Introduced in 2005

For the rel attribute of HTML link and anchor elements

Links under “nofollow” tag will not considered for the purpose of PageRank

Minimize PageRank leakage

PageRank is only one of the parameters involved in Google’s ranking of the answers to a given query.

Optimal computation of PageRank

In addition, I presented the technical soundness of a dynamic computational scheme taking place while changing the structure of the Web.