Pagerank is a measurement tool for checking the competitiveness of a website analyzed by Google. Google launched PageRank service in 1998, and Standford Duo deployed this searching algorithm. At that time, there was no other competitive search algorithm available in the market, and Google benefited from that a lot, which also made the founders Sergey Brin and Larry Page Billionaires.
Pagerank is a searching algorithm developed by Google and was later started being used by webmasters to judge the quality of a website regarding the backlinking and search engine optimization (SEO). The page rank value of any given website ranges from 0 to 10 points. The higher the PageRank, the more a website has a chance to rank on top pages in Google search engine. Pagerank also indicates the domain authority, and the high PageRank indicates high value and authority website which means if a high PageRank website links to another website with an anchor tag, the chances for another website of being crawled and indexed increases. This means that linking between pages and linking between websites matters a lot.
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It is better not to include links of too many external websites because it can hurt the website reputation and affect the ranking of your website negatively. However, internal linking or navigation is preferable as it is a win-win situation because the pages you are linking to are all your own pages and you have a better idea of what content you are linking to. However, you cannot guarantee the cleanliness, malware free and spam-free interface of other websites, and if somehow any website you are linking to is injected with virus or malware at any time, then chances exist that search engines penalize you for linking to bad neighbors.