It depends.
Credibility depends on your expectations about the piece of information as a whole, and the context in which you're using it.
I find that asking myself these questions helps me decide if information is credible to me. Note that there are no right answers to these questions. Answers are personal to you.
- How old is this information and does that matter?
- Does this information seem trustworthy to me?
- If this is an opinion piece, is it fact-based or totally coming out of left field?
- What kind of reaction do I have to this information?
- Can I identify an author?
- Do I trust the publisher of this information (could be a website, blog, magazine, corporation)?
- Does this source ask questions? Is it philosophical or curious or demanding?
- Is the source long enough to actually share good, meaty information?