"Who is the author?" is the root question. If you don't find one, turn your skepticism meter to the top of the dial. And use easywhois.com to find out who owns the site if there is no author listed. If the author provides a way to ask questions, communicate, or add comments, turn up the credibility meter and dial back the skepticism. When you identify an author, search on the author's name in order to evaluate what others think of the author - and don't turn off your critical stance when you assess reputation. Who are these other people whose opinions you are trusting? Is the site a .gov or .edu? If so, turn up the credibility a notch. If it helps, envision actual meters and dials in your mind's eye - or a thermometer or speedometer. Take the website's design into account - professional design should not be seen as a certain indicator of accurate content, but visibly amateurish design is sometimes an indicator that the "Institute of Such-and-Such" might be an obsessive loner.