filterTpl = new Array();
filterTpl[0] = "progid:DXImageTransform.Microsoft.AlphaImageLoader (src='images/nav/";
filterTpl[1] = ".png', sizingMethod='scale')";

function hoverOff(imageItem, itemSource) {
	if(imageItem.src) {
		imageItem.src = 'images/nav/' + itemSource + '.png';
	} else {
		imageItem.style.filter = filterTpl[0] + itemSource + filterTpl[1];
	}
}

function hoverOn(imageItem, itemSource) {
	if(imageItem.src) {
		imageItem.src = 'images/nav/' + itemSource + '_av.png';
	} else {
		imageItem.style.filter = filterTpl[0] + itemSource + "_av" + filterTpl[1];
	}
}