Is there a doctor reviewing the information on the site? 
Who is sponsoring the site? [Do a Whois search at &&url, Network Solutions. It gives the site administration information.] 
What is the motivation for the site? 
Health sites that are hawking goods or services often provide biased information. 
Some sites simply make mistakes. 
Some sites are better than others for certain subjects. 
Some search words work better than others to get the information you want. 
Check the date, some areas are fast-moving and quickly outdated. 
Seek many opinions, do not limit yourself to one source of information. 
Change some of the keywords in the search engine windows, do repeated searches. 
Do not give out personal information to websites; use a hotmail or yahoo or similar email address. 
Give a phony name, address and other information, if registration is required. 
ALWAYS talk with your doctor before making medical decisions. 
Bring to your doctor's a few pages of material, and the URLs. 
Some doctors think patients who find out about their illnesses are a pain 
Good doctors recognize that you not only are helping by gathering information, but also educating yourself and taking charge of your decisions. In summary, you are acting responsibly.