function chgsrc(wo,zu) {
		var cl = wo.className;
		if (cl.indexOf('aktiv') == -1) {
			var img_src = wo.src;
			if (zu == 'w') {
				var re = /_b/;
				new_src = img_src.replace(re,'_w');
			}
			else {
				var re = /_w/;
				new_src = img_src.replace(re,'_b');
			}
			wo.src = new_src;
		}
	}