This CSS will cause harsh black edges on transitioning PNGs to fade or blur to white in IE8 and IE7.

blur-png-images.css

.slideshow img {
	background: transparent;
	-ms-filter:"progid:DXImageTransform.Microsoft.gradient(startColorstr=#00FFFFFF,endColorstr=#00FFFFFF)"; /* IE8 */   
	filter: progid:DXImageTransform.Microsoft.gradient(startColorstr=#00FFFFFF,endColorstr=#00FFFFFF);   /* IE6 & 7 */      
	zoom: 1;
}