Look for websites that have the Hon Code - usually at the bottom of the page. It's a governing body that gives guidance http://www.hon.ch/HONcode/Patients/
As they say:
"The HONcode is not an award system, nor does it intend to rate the quality of the information provided by a Web site. It only defines a set of rules to:
- hold Web site developers to basic ethical standards in the presentation of information;
- help make sure readers always know the source and the purpose of the data they are reading."