function PNG_swap( element_id, image_name )
{
	var element = document.getElementById( element_id );
	if (element.nodeName == 'IMG') {
		element.src = image_name;
	} else {
		var filter = element.style.filter;
		var src_start = filter.indexOf( "(src='" );
		src_start += 6;
		src_end = filter.indexOf( "'," );
		left = filter.substring( 0, src_start );
		right = filter.substring( src_end );
		element.style.filter = left + image_name + right;
	}
}