function promptGoToPage(index_no) {
	var page_no = prompt('Go to which page?');
	if (page_no === null) {
		return;
	}

	var index = window['page_index_' + index_no];
	page_no = parseInt(page_no);

	if (isNaN(page_no) || page_no < 1 || page_no > index.num_pages) {
		return alert('Invalid page number.');
	}

	var offset = index.wildcard_url.indexOf('start=') !== -1 ? (page_no - 1) * index.per_page : page_no;
	window.location.href = index.wildcard_url.replace('%d', offset)
}