Use Turabian 17.7 for citing online sources other than books or periodicals, such as Web sites.

Last, First. "Title of the Page." Title or Owner of the Site. URL (date accessed in            parentheses)

Tanner, Stephen. "The Story of a Chopin Piano." Chopin Foundation of the United States.
            http://chopinfound.brinkster.net/Atimo_s/news/TheStoryofChopin.pdf            
           (accessed February 1, 2008).