how do you determine credibility of information on the Internet?

Answer 1

Cross check everything. Check their source - their reference material. If possible have several different sources for the same information.
Its like when I was checking up on a new "Wonder Suppliment" I found that the only ones promoting the benefits as quoted on their advertising, were the people either directly or indirectly involved in selling the stuff. All refered to the exact same "study". When I cross checked with other medical sources, I found that the claims were vastly exaggerated, and though the suppliment did have some applications, it was far from the wonder drug that they promoted it as.

Answer 2

As you know, it can be pretty shaky. You have to evaluate the source of the info - for example, the website of a university, someplace like medline, or a site of a major well-known organization has a better shot of being reliable than a site that's somebody's personal site. Personal sites can have great info, but it's hard to tell whether it's reliable or not.

Your local librarian can probably help you evaluate websites if you are looking for info on a particular topic.