How an individual reasons from evidence to claims to arguments is often influenced by both rational and emotional factors, elements of one’s identity, and values and belief systems. Only by keeping your personal biases in check can one truly begin to evaluate information for credibility.
Authority established. Does the author have education and experience in that field?
Purpose/Point of view of source. Does the author have an agenda beyond education or information?
Publisher? Does the publisher have an agenda?
List of sources (bibliography). Is the evidence sound?
Year of publication. Does the year of publication effect the information?
The internet is a great place to find both scholarly and popular sources, but it's especially important to ask questions about authorship and publication when you're evaluating online resources.
If it's unclear who exactly created or published certain works online, look for About pages on the site for more information, or search for exact quotations from the text in Google (using quotation marks) to see if you can find other places where the work has been published.
Click on the above link to visit UCBerkeley's guide on how to effectively evaluate webpages to use as sources in your research project. (First, check with your professor to make sure you are allowed to use webpages as sources.)
*Internet sources are very different from the library database's scholarly sources, which are accessed online via the library's homepage.
Marshall University Libraries pays for online databases so that students, faculty, and staff can access credible information for free. Nearly all of the information in the library databases is not available on the internet (or, if it is available, you will likely be asked to pay money to access it).