Evaluate graphics using these criteria:
Authority - What level of credibility does the author hold?
Bias - What is the author's purpose in providing the information?
Accuracy - Are you able to cross-check facts?
Currency - Is this the most up-to-date information available?
Content Scope - Is the breadth and depth of the information appropriate for your assignment?
Don't judge a graphic by the domain extension:
Domain extensions (.com, .org, .edu, etc.) tell you something about graphics, but they don't necessarily reflect the reliability of information. A lot of industry graphics will be found on .gov sites.