Google Page Rank

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1. Google Page Rank

PageRank is a link analysis algorithm, developed (and ever developing) by Google for their internet search engine. It is named after Larry Page, the cofounder of Google. PR algorithm assigns a numerical weighting to each element of a hyperlinked set of documents, such as the World Wide Web, with the purpose of "measuring" its relative importance within the set. Google PageRank is probably one of the most important algorithms ever developed for the Web. With billions of existing pages and millions of pages generated every day, the search issue in the Web is more complex than you probably think it is. But how is it actually done? How does Google PageRank work, which factors do have an impact on it and which don’t? And what do we really know about PageRank?

1.1. What is it?

PageRank is one of the methods Google uses to determine a page’s relevance or importance. Google uses many factors in ranking. Of these, the PageRank algorithm might be the best be the best known. PageRank evaluates two things: how many links there are to a web page from other pages, and the quality of the linking sites. With PageRank, five or six high-quality links from websites such as www.cnn.com and www.nytimes.com would be valued much more highly than twice as many links from less reputable or established sites.
PageRank has only ever been an approximation of the quality of a web page and has never had anything to do with the measuring of the topical relevance of a web page. Topical relevance is measured with link context and on-page factors such as keyword density, title tag, and everything
else.

1.2. How Does PageRank work?

No one knows for sure how PageRank is currently calculated by Google. All the facts associated to it are results of various studies and research conducted time to time by various companies, agencies and individuals. Let’s put those facts straight.

• - The core Google PageRank algorithm “distributes” it’s established PR across all of the outbound links. Put differently, 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.
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  - PageRank uses the link structure as an indicator of an individual page’s value. Google interprets a link from page A to page B as a vote, by page A, for page B. Google looks at considerably more than the sheer volume of votes, or links a page receives; e.g. 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”.

1.3. Which factors do have an impact on PageRank?

• - Each inbound link is important to the overall total except banned sites. “PageRank is a form of a voting system. A link to a page is a vote for that page. Higher PageRank pages are viewed by Google as more important. Their votes are given more value by Google — much more value, in some cases. In general, the more voting links, the stronger the PageRank.”
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  - Adding new pages can decrease Page Rank. The effect is that, whilst the total PageRank in the site is increased, one or more of the existing pages will suffer a PageRank loss due to the new page making gains. Up to a point, the more new pages that are added, the greater is the loss to the existing pages. With large sites, this effect is unlikely to be noticed but, with smaller ones, it probably would.
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  - Page Rank can decrease. You can lose some important links that are no longer linking to your site. PR loss can also occur if some of your linking partners also experience a drop in their own PR, possibly setting off a chain reaction of lower PageRank all through the immediate linking network.
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  - Links from and to high quality related sites are important. The more closely related the pages, the higher the PageRank amount transferred. Linking to high quality sites shows the search engines your site is very useful to your visitors. Linking only to high quality content sites will give your site an edge over your competition.
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  - Incoming Links from popular sites are important. If pages linking to you have a high PageRank then your page gains some part of their reputation.
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  - Site can be banned if it links to banned sites. Be extremely careful of any out-going links from your site. Don’t link to bad neighborhoods (link farms, banned sites, etc.) Google will penalize you for bad links so always check the PageRank of the sites you’re linking to from your site.

1.4. Which factors don’t have an impact on PageRank?

• - Frequent content updates don’t improve PR automatically. Although Google might send crawlers more frequently to analyze your site, what is more significant are links pointing to your site.
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  - Content is not taken into account when PageRank is calculated. Content is taken into account when you actually perform a search for specific search terms.
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  - High PageRank does NOT guarantee a high search ranking for any particular term. If it did, then PR10 sites like Adobe would always show up for any search you do. They don’t.
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  - Wikipedia Links don't improve Page Rank. Wikipedia implemented a no-follow rule, indicating that outbound links should not be followed by search engine spiders.
• - Sub-directories don’t necessarily have a lower Page Rank than root-directories. Depending on the popularity of a website your subdirectories can have a higher PageRank than the root pages