The credibility of an author is a key element in determining the quality of sources you have located. There are several ways of determining if an author/creator is credible. You will often find a few key experts on a subject and see their names repeatedly.
To find the authority for articles there are more steps involved. First note the publication the article appeared in, check with UlrichsWeb to see if the publication is a newspaper, magazine, or a refereed journal. Newspapers and magazines are popular sources often written by staff writers not experts in the field. Academic Journals are written by experts and evaluated by peers (peer-reviewed journals) offering a level of credibility to the article. Academic articles will usually include their credentials or affiliations. References (footnotes, endnotes, etc.) will also implicate authority, by offering other scholars mentioned in the article. Just because a journal is prominent in the field does not guarantee that its published work is credible. Author affiliation with a specific publisher, society, or institution is also not a finite indication of reliability. Most databases will allow you to search the author of one article with a simple click on the author of the original article, this can show an author’s publication record and area of expertise.
Search Google Scholar for the author and article. Google Scholar provides a feature that will tell you how often the article has been cited by others (a high number of citations is a good indicator that the author is credible). Another feature in Google Scholar is the ability to link to an author's profile.
This document offers examples of the types of sources related to art history that you might find as you research. They are listed hierarchically from the most scholarly and reliable at the top and highlighted in green, to the least reliable at the bottom.
Websites are the least credible of resources and generally should not be used for academic research. Author or creator information is often not included or is hidden on an “About” page. Check the page for updated information and to see who hosts the site (a .com, .edu, .gov, etc.). Googling can be a way to double-check the information about a subject or author but should not be the only research location.