Try to look at who wrote the information, if they are affiliated with any organization or have special knowledge or expertise.
See if you can determine when it was written and published. Check to make sure the links are not broken.
Determine what the purpose of the site is, how the information is written, and who it may be written for.
Check for bibliographic citations, links to other sites, or other means for you to verify information on the site. Look for any errors in the information given, or misspellings.
If you are still unsure, you can contact your Subject Librarian with further questions.