var loadflag = false;

function book() {
	loadflag = true;
}
function bookon() {
	if (loadflag) {
		id_show = 'bookbox';
		document.getElementById(id_show).style.visibility = "visible";
	}
}
function bookoff() {
	if (loadflag) {
		id_show = 'bookbox';
		document.getElementById(id_show).style.visibility = "hidden";
	}
}