Google’s quest for the perfect search engine saw the development of PageRank technology, which helped provide users with more relevant search results.
PageRank was the technology that enabled Google to move away from matching keywords on a site to incorporating the site's popularity in to its search rankings.
PageRank is a calculation that determines a page’s popularity by analysing the number of links to that page. The greater the number of links, the more popular the page is deemed to be and the higher the PageRank.
Google took this a step further and looks at how popular the linking pages are. If those pages themselves have a high number of links then this will boost the Page Rank score of the original. So both quantity and quality of links is required for a high PageRank score.
While other search engines were struggling to cope with the growth in sites on the web, this increase aided Google by providing more data for the Page Rank score which boosted the quality of the search results. 1
PageRank is arguably better understood visually. A picture says a thousand words.
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