For web sources, give the author (if known), the title of the page, the complete URL (= the address of the web page, which you can get in the menu bar of your browser or at the very bottom of your browser page in the status bar if you're working off of the CST online resources on the front page of the class website), and the date on which you accessed the site.

So for example:

Joseph Incandela, "Catholic Social Thought Online Resources," Available:
http://www.saintmarys.edu/~incandel/cst.html (September 27, 2009).