When evaluating a website, consider the site's URL (Uniform Resource Locator), a protocol for specifying addresses on the Internet. The URL can tell you several things about the website: creator, audience, purpose, and sometimes country of origin.
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From this web address you can tell:
.com - Commercial
A company owns the site. A .com can be the company's actual Web site or it can be a Web space that a company sells to people. Commercial sites are often difficult to evaluate because companies may include educational information on portions of their sites. For example, the Duracell site information about sustainability and disposal. You must decided on a case-by-case basis whether a particular site's information outweighs its commercial / advertising agenda.
.org - Non-Profit Organization
If you use a non-profit organization's site, think about the organization's agenda and how it's likely to influence the way they present information.
.edu - Educational
A .edu site is from a college or university, such as the University of Washington's http://www.washington.edu. Usually, this means that the site has good information, but sometimes colleges and universities give Web space to students. Remember that the students may or may not check their facts when they put information up on the Web.
.gov - U.S. Government
These sites are produced by some part of the United States government (federal, state, county, or city government).
.mil - U.S. Military
These sites are produced by branches of the United States military (Army, Navy, Marines, Coast Guard, etc.)
.net Internet-Related Service
This means that the site has something to do with providing internet-related service. Local internet service providers will have .net as part of their addresses, although they might also be .com.
.k12 - K-12 School
These sites come from K-12 Schools (kindergarten through 12th grade) and can include pages created by teachers and students.
~ - Individual
If you see a tilde (~) in the Web address, you'll know that an individual created the page. Make sure that the individual cites their sources if you're considering to use the information in your research. Note: Universities offer Web space to their faculty, staff, and students. If you're studying a subject in which the individual whose page you're looking at is a prominent researcher, it's probably all right if she doesn't cite outside sources when she discusses the topic of her own expertise.
.uk United Kingdom
A domain suffix is the last part of a domain name and is often referred to as a "top level domain" or TLD, Popular domain suffixes include ".com," ".net," and ".org," but there are dozens of domain suffixes approved by ICANN. May 6, 2011
ICANN coordinates the Internet's naming system, including the creation of domain suffixes.
"ICANN is a not-for-profit public-benefit corporation with participants from all over the world dedicated to keeping the Internet secure, stable and interoperable. It promotes competition and develops policy on the Internet's unique identifiers. Through its coordination role of the Internet's naming system, it does have an important impact on the expansion and evolution of the Internet."
-from ICANN's About page.