Evaluating the quality and authority of a website can be challenging. Here are a couple of resources that identify criteria and questions that you can impose upon a website in trying to ascertain its authorship, authority, and reliability.
Evaluating Web Pages:Techniques to Apply & Questions to Ask (University of California, Berkeley)
This guide centers around 5 key questions with various subquestions and critieria for each question.
Evaluating Web Sites: Criteria and Tools (Cornell University)
This resource identifies useful guidelines in assessing a website and also identifies several sets of criteria from other select sources.