Google is a search engine owned by Google, Inc. whose mission statement is to "organize the world"s information and make it universally accessible and useful". The largest search engine on the web, Google receives over 200 million queries each day through its various services.
Google uses an algorithm called PageRank to rank web pages that match a given search string. The PageRank algorithm computes a recursive figure of merit for web pages, based on the weighted sum of the PageRanks of the pages linking to them. The PageRank thus derives from human-generated links, and correlates well with human concepts of importance. Previous keyword-based methods of ranking search results, used by many search engines that were once more popular than Google, would rank pages by how often the search terms occurred in the page, or how strongly ***ociated the search terms were within each resulting page. In addition to PageRank, Google also uses other secret criteria for determining the ranking of pages on result lists.
Google not only indexes and caches HTML files but also 13 other file types, which include PDF, Word do***ents, Excel spreadsheets, Flash SWF, plain text files, among others. Except in the case of text and SWF files, the cached version is a conversion to HTML, allowing those without the corresponding viewer application to read the file.
Users can customize the search engine somewhat. They can set a default language, use "SafeSearch" filtering technology (which is on "moderate" setting by default), and set the number of results shown on each page. Google has been criticized for placing long-term cookies on users" machines to store these preferences, a tactic which also enables them to track a user"s search terms over time. For any query (of which only the 32 first keywords are taken into account), up to the first 1000 results can be shown with a maximum of 100 displayed per page.
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