Found this today, tried it and it seems to work just fine. Not much good if you want to render the PNG on a patterned background (or on a variety of different background colours), but OK if you are just using PNG as generic GIF replacements. The additional technique, described in brief at the bottom of the article will work better if you want to retain the transparency, but overall it seems more work than just saving the image from Photoshop as a GIF and then using an IE specific stylesheet.