Use common sense when judging a source concerning their boundaries. References are provided by the site. If print references, they can be evaluated the usual way. If references are links to other Internet documents, you're back at the starting point in evaluating the new reference. Not having references does not invalidate a source, consider what you are using the source for, the audience, and the nature of the subject the source concerns.
Many Web sites contain links to other documents or sites on the Web.
Follow a few of these links to see what kind of information the author associates with the site. On-line Journals that use refereeing by editors or others. This process is the same as for printed versions of their journals. Also, if you notice the use of bad grammar or misspelled words in a web site, it is a sign for caution. Whether the errors come from carelessness or ignorance, neither puts the information or the writer in a favorable light.