Confirm Alert Box
The author notes, "The JavaScript confirm alert box differs from a regular alert box in that it provides two choices for the user, OK and Cancel. Typically, you�ll see confirmation boxes utilized on links where the destination is outside the domain of the page you�re currently on or to alert you of potentially objectionable material. The following example will display a confirmation alert box when either a link or form button is clicked. Once either OK or Cancel are selected an alert box will follow to display which was chosen."