Hello Chris, Yes, the same problem here but the warning message is different: Message: 'offsetParent' is null or not an object Line: 2145, Char: 4, Code: 0 URI: http://www.ajaxavailabilitycalendar.com/calendar/ac-includes/js/mootools-1.2.4.2-more.js I am using IE8. And when I turn on the "compa...