The most likely reason is that you're referencing the file incorrectly. Make sure that you have the JavaScript file in the same directory as the HTML file and make sure that you're referencing the file in a way consistent to its case. EventUtil.
js and eventutil.
js are considered different files on a Unix system (but are the same on a Windows system).
Nicholas C. Zakas
Author, Professional JavaScript for Web Developers (ISBN 0764579088)
http://www.nczonline.net/