A modal dialog is a box or window that appears in MSIE without opening a new
instance of the browser object. The modal also does not take space in the
taskbar, it is linked to the window object that spawned the modal.

A modal must be closed before focus can be given back to the opening window.
A modeless dialog, appearing the same as a modal dialog, allows focus to be
directed back to the window that spawned it, thus the difference between the
two dialog objects.