Make sure to look for sites that end in .gov or .edu, it means that the government or an educational institution is standing behind that information. Usually when you see .org, this is provided by a non-profit organization.
Websites that display ads and get revenue this way can be “specialists” at developing patient-friendly websites and information that is presented well but may be trying to sell you snake oil. Information at non-profit or educational websites can be very stiff and patient unfriendly– they’re just doing their best that they can with the money they have.
Sites like www.WebMD.com and www.drugs.com are excellent resources.