Here are some things to look for when you're evaluating a Web site or a source other than an article found through a library database, book, etc.
Currency
Simply speaks to the recency of published information. Is the information outdated for the topic you're studying?
Authorship
Locate the author of a publication, Web site, etc. Is he or she qualified to speak on a given topic?
Sponsorship
Sometimes a sponsor will have a hidden agenda. This is something that I learned when looking for the Center for Consumer Freedom (CCF) in SourceWatch.
Purpose/Audience
Ties in with authorship and sponsorship. What is the intent of the Web site or publication?
Accuracy
Is the information found on a given Web site, book, etc. accurate? If an author lists the wrong dates for World War I, the accuracy of the remaining information is thrown into question.
From:
Hacker, Diana, and Barbara Fister. (2009). "Tips for Evaluating Sources." Bedford/St. Martin's.com. Bedford St. Martin's, n.d. Web. 19 Aug. 2011. Retrieved from http://www.dianahacker.com/resdoc/tips.html.
Quaratiello, Arlene, and Jane Devine. The College Student's Research Companion: Finding, Evaluating, and Citing the Resources You Need to Succeed. New York: Neal-Schuman, 2011.