01 - simple rollover image with javascript
This is a simple simple rollover image, it has no features like preloading the image into a Javascript object or anything fancy like that...

Did my ultra-primitive rollover effect work?

Yes, it did. But since the image for the 'over' state of the button is not preloaded, the very first time I mouse over it, it's going to dowload it from the server and that's going to take some time. This is a drawback.