When using online resources, be sure to record as much information as possible including the date you accessed the site, any authors, and the precise URL. If you are referencing a scientific article found online (ie through Google) it is best to figure out where it was originally published and record your citation from the original source.
To keep up with references and appropriately cite them in papers and bibliographies, consider one of these tools. Each will copy article, book and other citations from databases into a single location that you can manage. Style options include CSE, APA, MLA, Chicago and many others.