If sources are not validated, you may see a disclaimer at the bottom of the screen that absolves the site managers from incurring any liability for errors in what is presented there. Using non validated information is very risky when doing scholarly work. For the health professions, there may be many companies that maintain web sites. These may be related to drugs, patient care products, journals, etc. The web searcher should critically reflect upon the possibility of product bias in these sites.
Addresses containing .edu represent educational institutions.
The information on these sites is usually traceable to the contributors. Their names may be on faculty rosters or traceable to published scholarly research.