CSS Code:
#btn{
background: url(transparent.png) no-repeat;
filter: alpha(opacity=0);
-moz-opacity: 0;
-khtml-opacity: 0;
opacity: 0;
}
I think there is a real solution here : http://www.viget.com/inspire/jquery-ie-png-24-ie-black-background-issue-solved/
In my case it solved the awefull black bg on my animated png image with transparent background. It worked like a charm. Tested on ie7+ I can't test ie6 for the moment.
Hope it will help every one :) Julien