I have known about the png format for a long time but I really did not have a reason to use it. I still see more problems with the size of graphics files. GIF and JPG work just fine for me. Since I like Mishoo's work, I read his article and learned about opacity and IE's lack of standard support for png. I still don't have anything I want to do with png but translucent objects are a nice feature you need png for. For more info check out the ALA article, Cross-Browser Variable Opacity with PNG: A Real Solution.