Animation button for website

What's a easy and fast way to make animated buttons for a website, like mouse roll over effects and such?

I had to do a website recently and had this problem too. Then I remembered in past website projects I did, I used photoshop.

What you do is:

1. Make the image or a row of menu button I am guessing, next to each other
2. Using the slice tool, slice it up into seperate buttons
3. Using Fail>Save As Web, save the image as a website
4. Change the image and repeat step 3, but saving the website in a different folder/file name
5. Go to the folder where the site is stored
   
6. Deleted everything else except for the images saved in the image folder and move them to your website project folder and use them
7. Program the animation as you would normally with jpegs

hope this helps or at least I hope I can remember this post to stop me wasting time in photoshop in the future.