CSS Image Transparency for IE, Mozilla and Safari
There is no single way to create a cross browser image transparency. This tutorial tells you how to make it work in 3 of the most popular browsers.
Very useful to know but its been around for years. Flickr uses this technology so unregistered users can’t save your pictures if you don’t want them to.
I much prefer using png’s and a little behavioral javscript. It also links a page with similar scripts not associated with css background images. I’ve never figured out why nobody uses this more often… It was posted 2 years ago.
Here’s another interesting related article - Sleight of hand.