function add_load_event(func) {
	var oldonload = window.onload;
	if (typeof window.onload != 'function') {
		window.onload = func;
	}
	else {
		window.onload = function() {
			oldonload();
			func();
		}
	}
}

// changes the opacity of an object 
function change_opacity(obj, op) {
	obj.style.opacity = (op / 100);
	obj.style.MozOpacity = (op / 100);
	obj.style.KhtmlOpacity = (op / 100);
	obj.style.filter = "alpha(opacity=" + op + ")";
}