Module 5 of the library's LINKS tutorialprovides information on "Using the Web". This screenwithin Module 5 explains the criteria you should use when evaluating the credibility and reliability of a web site.
You need to cite sources not just because it's required by your instructor or because you don't want to commit plagiarism (which are two very good reasons), but because you are contributing to research- you are an active participant in the research process
The research database,Gale Virtual Reference Library, provides credible background information on many topics. This database "provides access to online encyclopedias, almanacs, and specialized reference sources for multidisciplinary research."