02 - a better way to do rollovers with javascript
This time, I created two image objects, 'on' and 'off'. Their sources are the 'on' and 'off' states of the button, respectively. Then I just swap their sources out and they change.

Did my new and improved rollover effect work?

Yes, it did. This method is better because the images are preloaded with the page, so there's no waiting the first time you mouseover.