How do you create a rotating banner?

1) How do you create a rotating banner? Say 3 images in total changing
every 4 seconds?
2) Or whenever a person visits or refreshes a page, you get a random image
so the site appears fresh, (same image for the time that they are on that
page?

I heard that the code below is dated? Any recommendations? The simpler
code the better at this point.

I found this article for a simple rotating banner and it seems to work
great. Any caveats with this code?
http://www.webniche.com/rotate_banners/rotate.html (tested and works fine)