function changebg(id, isOver)
{
	var elem = document.getElementById(id);
	
	var img = elem.style.backgroundImage;
	var name = img.substring(4, img.lastIndexOf("."));
	if (name.substring(name.length-1) == "_")
		name = name.substring(0, name.length-1);
	var ext = img.substring(img.lastIndexOf("."));
	ext = ext.substring(0, ext.length-1);
	
	if (isOver)
		elem.style.backgroundImage = "url(" + name + "_" + ext + ")";
	else
		elem.style.backgroundImage = "url(" + name + ext + ")";
}