Review the criteria about the audience of a secondary scholarly work. Few websites today are peer-reviewed, attempt the rigorous criteria of methodology of printed scholarly works or seriously try to advance scholarship. Still, many websites are serious works of reliable secondary (analytical) scholarship.
How can you tell if a printed secondary work is scholarly or popular?
Who is the author? Are his or her credentials stated and are they appropriate?
Evaluating electronic resources
Check out this site from the Cornell University Library.