Challenge as the Largest Search Engine In the paper, the authors mentioned that some advertisers attempted to gain people’s attention by taking measures meant to mislead automated search engines. The idea and algorithm of PageRank, which is used to sort the search result list to improve the quality of searching, was brought forward in the paper. PageRank has proved to be effective and did solve the problem. That was also one of the reasons why Google became such a successful search engine later. However, a few years after the page was published, Google became the largest search engine. It has brought and is still bringing a huge amount of visits for websites, many of which count on the traffic to make profits. Because of this, some advertisers now focus more on how to taking measures to mislead Google. These attempts are challenging Google’s search quality. Good and Bad Search Engine Optimization (SEO) The strategy of affecting the visibility of a website or a web page in a search engine's results is usually call “SEO” (search engine optimization). SEO techniques can be classified into two broad categories: techniques that search engines recommend as good designs, and those techniques of which search engines do not approve. Good SEO strategy usually helps to make the website better for users and search engines to visit and analyze. For example, if web masters cross-list related pages within their websites, and use more clear structure to display the contents, the websites can gain higher PageRank. Bad SEO goes the different way. As was described in the paper, a page with more pages point to it can gain a higher PageRank. To gather as many citations as possible, advertisers are using bots to post junk comments in forums and blogs with links to their websites. Another way to get a higher PageRank for certain key words is to put some related contents in some parts of the pages which are hidden for the human visitors but “visibl