12IntroductionPageRank was proposed by Larry Page and Serge Brin, the founders of Google. [1] PageRank is a link analysis algorithm used to determine the relative importance of a web page. Thus, a web page with a higher PageRank is considered more important and is more likely to be listed higher than a page with a lower PageRank.2Earlier Search EnginesThere were many search engines before Google. But unlike Google, most of them used simple web crawling techniques like reverse indexing and term frequency. Essentially, an inverted index is a data structure that points to every instance where the term appears, making searches relatively efficient and easy. When querying terms using reverse indexing, the search engine locates on which web pages those terms were found. Reverse indexing will rank the web page based on how the term was used. So, a web page with that term in the title or header would be more relevant than a web page with a high number of occurrences of that term. The term frequency was used more to reassure the relative nature of a web page rather than to rank the pages themselves. As people began to become more familiar with the Internet and how search engines were used, exploits were discovered. In particular, how the pages were classified. People have found it easy to get others to visit their websites, either by including the term in the title or header or by increasing the number of times that term appears in their web page. For example, people selling cars could easily exploit the weaknesses2 of reverse indexing by adding the word "cars" to their title and increasing the number of times the word appears in their regular text to fool the search engine. and make it rank their page higher. ..... middle of article...... Taher H. Haveliwala, Topic-Sensitive PageRank, Stanford University[3] Zolt an Gy ongyi, Hector Garcia-Molina and Jan Pedersen, Combating Web Spam withTrustRank, Stanford University, Pages 577-578 [4] Adam Bilter, What is PageRank?, retrieved March 17, 2014 from http://checkpagerank.net/blog/pagerank/what-is-pagerank.php [5] Ian Rogers, IPR Computing Ltd., The Google PageRank Algorithm and How It Works, retrieved March 20, 2014 from http://www.cs.princeton.edu/chazelle/courses/BIB/pagerank.htm[6] Jeffrey D. Ullman, PageRankChapter 5, Link Analysis Pg 161-173 [7] Webmaster Resources and SEO Tips, Google - Pros and Cons of PageRankRetrieved March 20, 2014 from http://web-master-seo.blogspot.com/ 2008/03/google-pagerank-benefits-and.html [8] Amy N. Langville and Carl D. Meyer, Google PageRank and Beyond: The Science of Search Engine Ranking