Good researchers always ask at least these questions about every website they might want to use for research:
Questions about the AUTHOR:
1. WHO wrote it? The author might be one person, but it's important to know what institution (business, newspaper, university, organization, etc. takes responsibility for the website).
2. QUALIFICATIONS: What kind of expertise or knowledge do the authors say they have that qualifies them to talk about the topic?
3. REPUTATION: What do other people say about how trustworthy they are? (Google them and find out)
Questions about the TEXT:
1. PURPOSE: Why are they telling us this? No one creates a website by accident. Understanding what their purpose is helps us understand their point of view and the audience they are writing for.
2. CREDIBILITY: How strong and logical is their argument?
3. EVIDENCE: What kind of evidence is given, and where is it from? Do I trust those sources?
If you want any professor to accept your use of a website as a resource, you should be able to answer all of these questions clearly to show why you believe the website is a good source of information.