There are many authoritative websites that have good information. There are a lot that don't. You can usually find reliable information at Museums, Galleries, and Artists' websites. Universities, U.S. Government and Research Libraries are also good places to find information on artists. Knowing that, it's safe to use Google as a place to start to find Internet Sources.
Wikipedia is not considered a good information source. However, the references and external links lists at the bottom of each article can lead you to trustworthy sites.