How to load the roll over image menu from client and not from server side?

[askjames02]

I know how to make a ROLL OVER MENU, but the problem is the image is loading
from the server side.

What i want is to load all the images into memory so that when i hover the mouse the image is not fetch from the server but from on the client side.

for example this one.
http://www.drwbarker.com

-is this they called caching?

thanks in advance.

[askjames02]

or where can i find an example codes for this?