Wednesday, October 8, 2008

Introducing PageRank

In a nutshell, PageRank (PR) measures the quantity of incoming links to a given
web page and their relative strength. When one page links to another, it “casts a
vote” for that page in the form of a PageRank value.

In general, the more links you have that point to your site the better, as this increases
the PageRank of the page being linked to. The number of links that point to a site is
also sometimes called link popularity.

However, the amount of PageRank value these links “forward” on to your site, and
hence the amount that is used in the Google PageRank calculation, is diluted by the
presence of other links on the same page. This is where link strength comes into

The greater the number of other links on a page, the weaker the strength of each
individual link. Each link is essentially a “vote” for the page being linked to, and the
strength of that “vote” is divided equally among all other links on the page. Which
means, all other things being equal, if someone has a link to your site on their page
with 100 other links, you won’t get any appreciable value from that link in the overall
calculation, UNLESS the page has a very high PageRank score. Confused? All will
be explained in the next chapter!

Tip: There is some confusion around whether you should spend more time getting a
few links from pages with high PageRank or whether to get lots of links from pages
with low PageRank. Rather than fret over this, my advice is simple - just acquire
links! Today’s site with a low PageRank can be tomorrow’s site with a high
PageRank, and even vice versa.

Note: In mid-November 2003, Google introduced a major algorithm change during
the so-called “Florida Update” that changes the way Google ranks certain websites.
It is believe these changes mainly involve how PageRank is computed – more
accurately that PageRank is being phased out by a new “LocalRank” system of
computing PageRank dynamically on the fly. At this writing, this new algorithm is still
changing, with some of the effects not well understood. For more information, see
the applicable section Appendix D – About the Florida Update”.