SEO Techniques: Google PageRank & Search Engine Optimization

Google PageRank
PageRank is a numeric value that represents how important a page is on the web. PageRank is one of the methods Google uses to determine a page’s relevance or importance. PageRank is Google's way of deciding a page's importance. It matters because it is one of the factors that determines a page's ranking in the search results. It isn't the only factor that Google uses to rank pages, but it is an important one.

Google interprets a link from page A to page B as a vote, by page A, for page B. Google looks not only at the sheer volume of votes; among 100 other aspects it also analyzes the page that casts the vote. However, these aspects don’t count, when PageRank is calculated. Not all links are counted by Google. For instance, they filter out links from known link farms. Some links can cause a site to be penalized by Google.

How Does PageRank Work?
PageRank is only one of numerous methods Google uses to determine a page’s relevance or importance. PageRank is based on incoming links, but not just on the number of them - relevance and quality are important (in terms of the PageRank of sites, which link to a given site). Not all links weight the same when it comes to PR. If you had a web page with a PR8 and had 1 link on it, the site linked to would get a fair amount of PR value. But, if you had 100 links on that page, each individual link would only get a fraction of the value. Bad incoming links don’t have impact on Page Rank. Ranking popularity considers site age, backlink relevancy and backlink
duration. PageRank doesn’t. Content is not taken into account when PageRank is calculated. PageRank does not rank web sites as a whole, but is determined for each page individually. Each inbound link is important to the overall total. Except banned sites, which don’t count. PageRank values don’t range from 0 to 10. PageRank is a floating-point number. Each Page Rank level is progressively harder to reach.

No one knows for sure how PageRank is currently calculated by Google. PageRank is believed to be calculated on a logarithmic scale.PR(A) = (1-d) + d(PR(t1)/C(t1) + … + PR(tn)/C(tn)). “That’s the equation that calculates a page’s PageRank. In the equation ‘t1 - tn’ are pages linking to page A, ‘C’ is the number of outbound links that a page has and ‘d’ is a damping factor, usually set to 0.85.”

Google calculates pages PRs permanently, but we see the update once every few months (Google Toolbar).

Not all links weight the same when it comes to PR. If you had a web page with a PR8 and had 1 link on it, the site linked to would get a fair amount of PR value. But, if you had 100 links on that page, each individual link would only get a fraction of the value. Bad incoming links don’t have impact on Page Rank. Ranking popularity considers site age, backlink relevancy and backlink duration. PageRank doesn’t. Content is not taken into account when PageRank is calculated. PageRank does not rank web sites as a whole, but is determined for each page individually. Each inbound link is important to the overall total. Except banned sites, which don’t count. PageRank values don’t range from 0 to 10. PageRank is a floating-point number. Each Page Rank level is
progressively harder to reach.

Factors affect Google PageRank:
1. Efficient internal onsite linking has an impact on PageRank.
2. Related high ranked web-sites count stronger. But: “a page with high PageRank may actually pass you less if it has more links, because it’s spread too thin.”
3. Links from and to high quality related sites have an impact on Page Rank.
4. Multiple votes to one link from the same page cost as much as a single vote.
5. Each inbound link is important to the overall total. Except banned sites.
6. Adding new pages can decrease Page Rank.
7. Links from and to high quality related sites are important.
8. Incoming Links from popular sites are important.

Factors don't affect Google PageRank:
1. Frequent content updates don’t improve Page Rank automatically. Content is not part of the PR calculation.
2. High Page Rank doesn’t mean high search ranking.
3. DMOZ and Yahoo! Listings don’t improve Page Rank automatically.
4. .edu and .gov-sites don’t improve Page Rank automatically.
5. Sub-directories don’t necessarily have a lower Page Rank than root-directories.
6. Wikipedia links don’t improve PageRank automatically (update: but pages which extract information from Wikipedia might improve PageRank).
7. Links marked with nofollow-attribute don’t contribute to Google PageRank.