If the guy sitting next to you on a bus tells you he believes you have heart problems, you wouldn't pay much attention but when your doctor tells you, that is significant. Likewise, on the Internet you should never ask for, or consider a diagnosis of a medical condition. That doesn't mean you can't get any useful information on your health from the Internet however. The Mayo Clinic is one of the world's best medical facilities and the information on their web site is backed by that reputation.
Consider the person answering the question's motive. If they're promoting a product or service, that is a good reason to be skeptical. Also consider their experience. I have seen 10-12 year old children on this site offering advice on sex and marriage. They aren't always wrong but lack of experience is a good reason to consider the information suspect.
Most question and answer web sites like EHelp use a reputation score system. When readers find the information useful they click the up arrow and when they find inaccurate or unhelpful information, the down arrow. When you click on a person's name or logo, you can see their rep score. High reputation scores indicate that other users of the site have found that person's answers to be accurate and useful.
Bottom line, you assess information from the Internet just like any other information, you consider the source. The only difference is that the Internet most often offers a lot more to consider.
Answered Sep 04, 2013
Edited Sep 04, 2013