What would I use as the in-text citation for something like this?

"William Cockerill." Encyclopædia Britannica. 2009. Encyclopædia Britannica Online. 23 Jan
2009 <h://w.britannica.c/EBchecked/topic/123681/William-Cockerill>.

That's for the works cited page (bibliography page), not the in-text citation.

You need to have each source of information cited in TWO places:

1. the Works Cited page that is placed after the last page of your paper, and
2. in parentheses in the text of your paper, immediately after the quotation or paraphrase.

For example, this would go on the Works Cited page (with proper indentation for the second and following lines):

Du Bois, W.E.B. The Souls of Black Folk. Chicago, 1903. Project Bartleby. Ed. Steven van Leeuwen. Dec. 1995. Columbia U. 2 Dec. 2003
<www.cc.columbia.edu/acis/bartleby/dubois/>.

... and this would go immediately after the quotation or whatever:
(Du Bois)

The information in parentheses in the text needs to be as brief as possible. That's why there's a Works Cited page – for all the details of the listing.

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Here's a good place for information on citing in MLA format:
(Broken Link Removed)

Hold your cursor over the words CITING SOURCES in the left column and then click on whatever type of source you need help with. Many examples will show up. You will get two examples for each type of reference – one for the Works Cited page and one for the parenthetical (in-text) citation.

You can also see what a Works Cited page looks like – click on Sample Works Cited in the left column.