function show_dialog (html, title, modal, height, width) {
    if (!modal) modal = false;
    if (!height) height = 160;
    if (!width) width = 300;

    var $dialog = $('<div></div>')
	.html(html)
	.dialog({
	    autoOpen: false,
	    title: title,
	    modal: modal,
	    resizable: false,
	    width: width,
	    height: height
    });
    $dialog.dialog('open');
}