The authority of the source of information is dependant on two factors, the author and the publisher . Identifying the publishing body is much more important in evaluating web sites than with print publications that you find in the college library. Print publishers are in the business of publishing to make money by producing good publications. Any organization or individual can publish web sites. A site promoting tours to Italy is probably not the best place to look for Roman History.
Commercial enterprises design their pages to come up near the top of search engine lists.
There is almost no way to determine their completeness or bias. You must first decide if the information it conveys is accurate and trustworthy. Scholarly results and references should be presented in the style expected of that discipline. If not, the author may not be familira with the discipline. Check for spelling and grammar errors.