ARG!! For some reason this script isn't working; if you roll the mouse over the "Tongue Twisters" image and all the images above it, it says "Object doesn't support this property or method."
Tongue Twisters is on line 307.
The important part of the code is to keep the naming convention for the image objects. The on and off part of the name is what you need to worry about. This way you only need one function for all of your overs and offs instead of a separate function for each rollover like you have.
Let me know if you need me to explain the code better.