This document describes different types of timed observers in MooTools that can be used to periodically check for changes in form values and trigger callbacks. It explains a Module Timed Observer that checks a value every set number of seconds and triggers a callback on change. It also describes Form.Element.Observer and Form.Observer, which check single elements or entire forms respectively. An example is given of using Form.Observer to style a form differently when values are changed versus when the form is submitted.

1. Module Timed Observer