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Revision as of 01:00, 11 October 2007

Google is 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 several hundred million queries each day through its various services.

The search engine

PageRank

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 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.

Search results

Google not only indexes and caches (X)HTML files but also 13 other file types, which include PDF, Word documents, 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 (X)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.

Advanced search operators

Google's searches are not limited to reporting back indexed pages corresponding to the search query. A variety of advanced search operators can be used to perform more sophisticated queries. Some examples are included below:

• link: <URL> - returns the pages linking to the specified URL.
• site: <URL> - restricts the returned hits to a specific website
• define: <query> - returns Google glossary definition for the query term
• info: <URL> - returns information about the queried site.
• filetype: <filetype> - restrict the results of the search to a particular filetype extension e.g. doc, txt, jpg.
• related: <URL> - returns similar / related websites

A full listing of Google's advanced operators can be located here .

Non-Web sources of data

Despite its immense index, there is also a considerable amount of data in databases, which are accessible from websites by means of queries, but not by links. This so-called deep web is minimally covered by Google and contains, for example, catalogs of libraries, official legislative documents of governments, phone books, and more.

Google optimization

Since 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 tags, H1 heading tags and image alt attributes) and "Off Page Optimisation" 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 tag and the body copy (note: the higher up in the page, 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.

One "Off Page Optimisation" technique that works particularly well is Google selling in which websites link to another site using a particular phrase in the anchor text, in order to give the site a high ranking when the word is searched for.

The Google webmaster guidelines were published for website owners who would like to raise their rankings when using legitimate optimization consultants.

Uses of Google

A corollary use of Google — and other Internet search engines — is that it can help translators to determine the most common way of expressing ideas in the English language (and other languages). This is generally done by doing a 'count' of different variants, thereby establishing which expression is more common. While this approach requires careful judgement, it does improve the ability of non-native translators to use more idiomatically correct English expressions.

Google dance

Google dance refers to the period of time when Google indices are tuned. This will often cause both a fluctuation in index size as well a significant change in a web site's search result position.

Search engine features

Besides the main search engine feature of searching for text, the search engine can be used as a calculator, currency converter, dictionary and many others useful tools.

Error messages

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Some searches will give a 403 Forbidden error with the text

"We're sorry...

... but your query looks similar to automated requests from a computer virus or spyware application. To protect our users, we can't process your request right now.

We'll restore your access as quickly as possible, so try again soon. In the meantime, if you suspect that your computer or network has been infected, you might want to run a virus checker or spyware remover to make sure that your systems are free of viruses and other spurious software.

We apologize for the inconvenience, and hope we'll see you again on Google."

The suggestion that the user's computer may be infected is often incorrect. The screen was first reported in 2005 and was a response to the heavy use of Google by Search Engine Optimisation companies to check on ranks of sites they were optimising. The message may also be triggered by high volumes of different searches from a single IP address. The block is removed after a day.

International

Google is available in many languages and has been localized for many countries.

Languages

Countries

Search products

In addition to its tool for searching webpages, Google also provides services for searching images, Usenet newsgroups, news websites, videos, searching by locality, maps, and items for sale online. In 2006, Google has indexed over 25 billion web pages, 1.3 billion images, and over one billion Usenet messages. It also caches much of the content that it indexes. Google operates other tools and services including Google News, Google Suggest, Froogle, Google Maps, Google Co-op and Google Desktop Search.

There are also products available from Google that are not directly search-related. Gmail, for example, is a webmail application, but still include search features; Google Browser Sync does not offer any search facilities, although it aims to organise your browsing time.

Google games

• In Googlewhack attempt to find two words that produce exactly one search result.
• In Googlefight, pit two keywords against each other to find which one has more results.

See also

• elgooG
• Googlewhack
• History of Google
• Peter Norvig
• List of Google services and tools
• List of search engines

References

1. Search strategies
2. Google Advanced Operators Cheat Sheet
3. Google Webmaster Guidelines
4. http://www.google.com/language_tools?hl=en

Further reading

• Google Hacks from O'Reilly is a book containing tips about using Google effectively. Now in its third edition. ISBN 0-596-52706-3.
• Google: The Missing Manual by Sarah Milstein and Rael Dornfest (O'Reilly, 2004). ISBN 0-596-00613-6
• How to Do Everything with Google by Fritz Schneider, Nancy Blachman, and Eric Fredricksen (McGraw-Hill Osborne Media, 2003). ISBN 0-07-223174-2
• Google Power by Chris Sherman (McGraw-Hill Osborne Media, 2005). ISBN 0-07-225787-3
• SEO for Google by Paul Bliss - an eBook that describes in precise detail the methods needed to get your site top rankings in Google for your keywords.

External links

• Google.com
• Use Simulator for Google Search - comprehensive visual and interactive reference tool and user guide.
• Hidden Google

• Internet search engines
• Google