URLs Explained

Anatomy of a Web address

A Uniform Resource Locator, also referred to by its initials - URL -- is the unique address used to identify a Web site. It is similar to a home address, used to identify someone's mailing address. It is often simply called a Web address and is, literally, the address of a file on the Internet.

Segments of a Web address

The following example Web address is a Web page of the Internet Corporation for Assigned Names and Numbers (ICANN). ICANN is an international nonprofit corporation assigned responsibility for overseeing the management of the Internet's domain name system (DNS).

http://www.icann.org/general/links.htm

Here is the breakdown of components that make up this URL.

http: The protocol or computer language a computer must "speak" in order to retrieve this file. It stands for Hypertext Transfer Protocol. You never need to type http:// to access a Web site, however in some browsers and operating systems, just typing the name of a URL (the second-level domain) without the top-level domain automatically launches a search.

www: The name of the host computer. www is the most common, but you will occasionally see others, such as dir.

icann: The second-level domain. The second-level domain in conjunction with the top-level domain makes up the domain name that corresponds to a specific address.

org: The top-level domain. There are currently 13 top-level domains available.

general: A directory, or folder, containing Web pages.

links: The name of the file, or specific Web page, to be retrieved.

htm: The extension of the file, similar to .doc, the extension used for Word documents. Most Web pages contain the suffixes .htm or .html, but other extensions are becoming increasingly common.

Top level domains

Here is a list of all top-level domain names now approved by ICANN.

.com - commercial business

.mil - U.S. military or affiliated agency

.edu - educational institution (e.g., college)

.net - large network

.gov - U.S. governmental agency

.org - U.S. nonprofit organization

.biz - business

.coop - nonprofit cooperative

.info - any Web site

.museum - museum

.pro - professional (e.g., doctors, lawyers)

.name - personal Web site

.aero - airline

For Web sites outside the United States, a two-character country code is used. For example, .ar is the code for Argentina, and .bt is the code for Bhutan. .us was not originally assigned to domain names in the United States, although it is often used to designate state and local government sites, including many public schools and libraries.

Domains

You need to be proficient with the domains in a Web address. For example, the Web site for the White House is www.whitehouse.gov; it has the .gov extension since it is a government institution. The Web address www.whitehouse.net leads to a hoax site that deliberately has the look and feel of an official U.S. government site.

Guessing URLs

If you can't find the home page of a well-known company or organization, try entering the name or abbreviation as the Web address. For example, the Web address for NASA is www.nasa.gov, the Nabisco Company's Web address is www.nabisco.com, and the Web address of the Bill & Melinda Gates Foundation is www.gatesfoundation.org.

Beware of potential pitfalls inherent in this technique. Not all companies' Web sites correspond to their names. You need to evaluate very carefully the sites that you retrieve. For example, if you are looking for the Web site for the General Agreement on Tariffs and Trade (GATT), typing www.gatt.org will take you to a hoax site. The real Web address is www.wto.org.

When in doubt, use a search engine to find and verify the correct Web site.