I\'ve seen a few fixes for allowing PNG images to have transparency in Internet Explorer 6, but I\'ve yet to find one that also allows you to set the background position in CSS.
This is a new technique that has popped up in the last month or so. From the page:
In this script image tags are supported, both with and without a blank spacer GIF, and background image PNGs may be positioned, as well as repeated, even if they're smaller than the content element they're in.