Pageranking

To fully understand pagerank and how it can be channeled or sculpted, we need to add one additional concept: pagerank transference.

The idea is that if you have a page with lots of pagerank that points to lots of other pages (let's say 20) each link gets 1/20th the pagerank of the originating page. If the page has a pagerank of 100, each link would get a transferred pagerank "vote" of 100/20, or 5. If that same page had only two outbound links however, then each link would get 100/2 or 50 points.

Clearly, the more outbound links you have on a page, the less benefit each resultant destination page sees as the originating page gains in popularity. This is a bit confusing, but think about it this way: If we have a Web page with 20 outbound links (e.g., links pointing to other pages, either on our own site or another site) and our pagerank jumps from 100 to 200, each of those destination pages gains an additional vote of 5. Not so much. If we only have two outbound links, however, each sees a jump of 50 as our own page gains in pagerank!

The obvious question is whether you can control the flow of pagerank so that you can have outbound links that don't get any votes?

You can. That's what's called the "nofollow" attribute and to see how it works we need to briefly sidetrack and talk about HTML. A hypertext link on a Web page has two elements: the destination URL and the text that's to be shown as clickable. It looks like this:
"a href="http://www.google.com/visit scenic Google.com (surrounded by carets) and ending with a "/a" (also bracketed by carets)

In this instance, "http://www.google.com//" is the target address where you'll be taken if you click on the words "visit scenicGoogle". You already know this if you're learning HTML, I'm sure.
To have a hypertext link not pass along pagerank, the secret is to add the nofollow attribute, actually a value to the "rel" (short for 'relationship') attribute. It ends up looking like this:
(open caret) a href="http://www.google.com//" rel="nofollow(end caret) visit scenic Google.com (start caret) /a (end caret).

Download ebooks on http://www.frenchtheory.com/ - See that post with different algorithms in metabole - See the journal French Metablog with today different posts - Jean-Philippe Pastor