"If you go to Google and type in a disease, you're going to get two-and-a-half-million pages. And it's very hard to filter out what's good and what's not good," says Naomi Miller, manager of consumer health information at the National Library of Medicine (NLM). "It's better to start with a site that you trust and then branch out from there."

MedlinePlus.gov, the NLM's consumer-friendly health website, is one such starting point that can guide you to other carefully vetted sites. Most .gov and .edu sites are trustworthy. Websites of major medical centers or professional societies, such as the American Academy of Neurology, can also be good sources. So can volunteer health organizations -- but, Miller cautions, "you have to look at what they are and what their purpose is -- do they just want to get your money?"

To judge a website's credibility, it's worth viewing the NLM's online tutorial, Evaluating Internet Health Information.