Check out these tips when deciding to use an online source. Always be skeptical.
Authority: Who is responsible for creating the web page? Is there a publisher or sponsor of the web page? Can you find information about the author and publisher?
Audience: Who is this web site created for? Is the content geared towards an age group or population group?
Accuracy: How does the information compare to other sources?
Content: What is the content of the web site: images, articles, a blog? The type of domain (.edu, .gov, .org) may provide some clues about the information. Can you detect a bias? Are there cited references?
Currency: How recent is the web site? Is there information on when it was last updated?