Helpful Tips from Purdue OWL:
MLA lists electronic sources as Web Publications. Thus, when including the medium of publication for electronic sources, list the medium as Web.
It is always a good idea to maintain personal copies of electronic information, when possible. It is good practice to print or save Web pages to keep your own copies for future reference.
Note on the Use of URLs in MLA:
MLA no longer requires the use of URLs in MLA citations. Because Web addresses are not static (i.e., they change often) and because documents sometimes appear in multiple places on the Web (e.g., on multiple databases), MLA explains that most readers can find electronic sources via title or author searches in Internet Search Engines.
Author. "Title of article or section in quotes" (if applicable). Title of Book in Italics with All Important Words Capitalized. Name(s) of editor(s) (if applicable). City of Publication: Publisher (if given) or n.p., date of publication (if given) or n.d. Name of Online Source. Web. Day month year of access.
* Note: Citations are single-spaced here, but be sure to double-space your Works Cited page.