When citing sources that you find on the Internet you only need to include a retrieval date if the information you viewed is likely to change over time.
Reference list citation:
Research. (n.d.). In Merriam-Webster. Retrieved April 6, 2012, from
How to use the Google Advanced Search to do more effective searches on the Internet. Created by Instructional Services, David L. Rice Library at the University of Southern Indiana.
DavidLRiceLibrary. (2010, January 15). Google advanced search.wmv [Video file]. Retrieved from http://www.youtube.com/watch?v=E_QHaWLxGX8