function toggle_visibility(obj,id) {
	var e = document.all ? document.all[id] : document.getElementById(id);

	if(e.style.display != 'block') {
		obj.src = '/css/images/minus.png';
		e.style.display = 'block';
	} else {
		obj.src = '/css/images/plus.png';
		e.style.display = 'none';
	}
}