Let's determine the aspects
While the Internet contains a virtually-unlimited wealth of information not found in traditional resources, this abundance also may hinder academic research. Anyone can make a website for little or no cost and publish to the world. This bypasses the usual publishing channels and allows opinions to be expressed which may not be credible. Traditional sources may be considered more authoritative on the whole by some for this reason. On the other hand, this widespread publishing ability gives nearly-immediate access to the myriad views of both the average person and the professional world without the limited scope or bias which may be found in books and newscasts.
In general, a major way to find whether an online source is credible is to determine how popular and authoritative the source is. If the site has a well-respected offline counterpart such as the New York Times or CBS, the site will be as credible as the original. For websites and authors which have little popularity, one must consider the credentials of the source -- if those are available and valid. Even though a website may be written in a professional or academic manner, the lack of a central body to determine its credibility may be a prohibitive factor for serious research