Actually as it seems to me the easiest solution would be to integrated
Here You can get a JavaScript, fixing all png's:
http://homepage.ntlworld.com/bobosola/
This will also work with myfaces. Disadvantage: Having much png's on the page slows the client down dramaticaly.
Another aproach:
http://www.koivi.com/ie-png-transparency/
I have not tried yet but this seems to be a faster solution. They do some trick with a transparent png.
the ie7 css and script tags http://dean.edwards.name/IE7 they fix a lot of other annoying issues as well (for me the most important one the probably deliberately broken CSS positioning in IE) and are rather unintrusive....
