First, you should always look at the URL. The address will have a tell-tale ending. Here is an excerpt from a great site (http://www.lesley.edu/library/guides/research/evaluating_web.html) that explains it best:
What does the URL (Web address) say about the producer of the web site, and its purpose? Look at the final syllable in the domain name. The first three sites below are all "White House" sites. Which is the official White House site? How can you tell? Note that all three sites are easily accessible in a web search for 'White House'.
Government agency: www.whitehouse.gov
Internet Service Provider: www.whitehouse.net
Higher education - www.lesley.edu. Other educational sites may appear with different domain names: www.whitehouse.gov/kids
Military site- www.navy.mil/
("tilde") Personal site - http://www.members.tripod.com/~DAdams/qkbrdinf.html
Organization; may be charitable, religious, or a lobbying group - http://www.rtda.org.
Some links about website evaluation:
Remember this is a research paper. It requires the "so what?" factor. You have to prove and analyze a point within your paper.
The question is, have you ever seen sites that claim validity only to find out that they were a hoax, satirical, or trying to get you to signup/ buy something?
Check out this site.... valid or not?