Some things to keep in mind as you're evaluating a website include:
- Who wrote it? What are their credentials? At a minumum, they should be art historians (have a Master's degree or PhD in Art History)
- Is the page part of a larger institution qualified to write on the topic (e.g. a major museum)
- Do they cite their sources? Can you verify what they are saying?
- Are they trying to sell you anything? (Not a good sign!)
- Does the site have a particular bias - expressing likes, dislikes (Again, not a good sign!)
Check out this more comprehensive evaluation guide:
Evaluating Websites - Questions to Ask (from UC Berkely)