function open_book(book_name, pagenum, userid, key) {
	if (pagenum == null) pagenum = 1;
	if (userid == null) { userid = 0; key = 'no'; }
	var w, h;
	if (screen) {
		w = screen.width;
		h = screen.height;
	} else {
		w = 1024;
		h = 768;
	}
	w -= 12;
	h -= 62;
	var subdomain = book_name.split('_', 1)[0];
	livebook = window.open("http://" + subdomain + ".livebook.dk/livebook.php?book=" + book_name + "&userid=" + userid + "&key=" + key + "&pagenum=" + pagenum, "livebook", "width=" + w + ",height=" + h + ",left=0,top=0,location=no,menubar=no,resizable=no,scrollbars=no,status=no,toolbar=no");
	if (livebook && window.focus) livebook.focus();
}