The yellow box on the right is a 32 bit PNG showing 256 levels of transparency in I.E. The Alpha Image Loader filter is used to force I.E. to display the image properly .

Methods of inducing I.E. to display full Alpha are found at:
www.alistapart.com/articles/pngopacity/
www.koivi.com/ie-png-transparency/
www.howtocreate.co.uk/alpha.html
www.youngpup.net/