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Google search is a Web search engine owned by Google, Inc., and is the most used search engine on the Web. Google receives several hundred million queries each day through its various services.[3] Google search was originally developed by Larry Page and Sergey Brin in 1997[4].
The search enginePageRankGoogle's algorithm uses a patented system called PageRank to help rank web pages that match a given search string.[5] The PageRank algorithm computes a recursive score for web pages, based on the weighted sum of the PageRanks of the pages linking to them. The PageRank derives from human-generated links, and is thought to correlate well with human concepts of importance. The exact percentage of the total of web pages that Google indexes is not known, as it is very hard to actually calculate. 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 associated 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, reported to be a number over 200.[6] Search resultsGoogle not only indexes and caches web pages but also takes "snapshots" of other file types, which include PDF, Word documents, Excel spreadsheets, Flash SWF, plain text files, online videos such as YouTube and much more.[7] Except in the case of text and SWF files, the cached version is a conversion to (X)HTML, allowing those without the corresponding viewer application to read the file. Users can customize the search engine, by setting a default language, using the "SafeSearch" filtering technology 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 and retain the data for more than a year. For any query, up to the first 1000 results can be shown with a maximum of 100 displayed per page. Non-indexable DataDespite its immense index, there is also a considerable amount of data available in online databases, which are accessible by means of queries but not by links. This so-called invisible or deep web is minimally covered by Google[8] and other search engines and contains, for example, catalogs of libraries, official legislative documents of governments, phone books, and other content which is dynamically prepared to respond to a query. Google optimizationSince Google is the most popular search engine, many webmasters have become eager to influence their website's Google rankings. An industry of consultants has arisen to help websites raise their rankings on Google and on other search engines. This field, called search engine optimization, attempts to discern patterns in search engine listings, and then develop a methodology for improving rankings. As Google's algorithms and results have gained the trust of web users, commercial websites will profit from subverting these results by artificially inflating their rankings. Some search engine optimization firms have attempted to inflate specific Google rankings by various artifices, and thereby draw more searchers to their client's sites. One of Google's main challenges has been to weaken some of these attempts by reducing the ranking of sites known to use them. Search engine optimization encompasses both "on page" factors (like body copy, title elements, H1 heading elements and image alt attribute values) and Off Page Optimization factors (like anchor text and PageRank). The general idea is to affect Google's relevance algorithm by incorporating the keywords being targeted in various places "on page", in particular the title element and the body copy (note: the higher up in the page, presumably the better its keyword prominence and thus the ranking). Too many occurrences of the keyword, however, cause the page to look suspect to Google's spam checking algorithms. Google has published guidelines for website owners who would like to raise their rankings when using legitimate optimization consultants.[9] Functionality
The Google search engine has many intuitive features making it more functional. This could have played a role in making it as popular as it is today. Google is one of the top ten most-visited websites today[10]. Some of its features include a definition link for most searches including dictionary words, a list of how many results you got on your search, links to other searches (e.g. you misspelled something, it gives you a link to the search results had you typed in the correct search), and many more. It is unknown whether functionality, speed, or luck brought it its peak status. Search syntaxGoogle's search engine normally accepts queries as a simple text area, and breaks up the user's text into a sequence of search terms, which will usually be words that are to occur in the results, but may also be phrases, delimited by quotations marks ("), qualified terms, with a prefix such as "+", "-", or one of several advanced operators, such as "site:". The Google Help Pages document all of these additional queries. Google's Advanced Search web form gives several additional fields which may be used to qualify searches by such criteria as date of first retrieval. All advanced queries transform to regular queries, usually with additional qualified terms. Query expansionGoogle applies query expansion to the submitted search query, transforming it into the query that will actually be used to retrieve results. As with page ranking, the exact details of the algorithm Google uses are deliberately obscure, but certainly the following transformations are among those that occur:
"I'm Feeling Lucky"Google's homepage includes a button labeled "I'm Feeling Lucky". When a user clicks on the button the user will be taken directly to the first search result, bypassing the search engine results page. The thought is that, if a user is "feeling lucky", the search engine will return the perfect match the first time without having to page through the search results. According to a study by Tom Chavez of "Rapt", this feature costs Google $110 million a year as 1% of all searches use this feature and bypass all advertising.[11] Search engine featuresBesides the main search engine feature of searching for text, the search engine can also be used as a calculator, base, unit and currency converter, dictionary and many other useful tools. Error messagesSome searches will give a 403 Forbidden error with the text
sometimes followed by a CAPTCHA prompt.[12] The screen was first reported in 2005, and was a response to the heavy use of Google by search engine optimization companies to check on ranks of sites they were optimizing. The message may also be triggered by high volumes of different searches from a single IP address. Google apparently uses the Google cookie as part of its determination of refusing service.[13] The block is generally removed after a day.[citation needed] InternationalGoogle is available in many languages and has been localized for many countries[14]. LanguagesThe interface has also been made available in some languages for humorous purpose:
Domain namesIn addition to the main URL Google.com, Google owns 160 domain names for each of the countries/regions in which it has been localized.[14] As Google is an American company, the main domain name can be considered as the U.S. one though the gTLD .com can be used by any company in the world (not only those from the United States). Google.us does exist but is only a redirection to google.com because dot-US is by far less common than dot-com in the United States. An example is Google.ca or Google.com.au. List of domain names
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