I have been thinking about the best way to notify the user of errors
while keying.

1. verbal, the user can fix the error while the voice continues.  Java
does not have a decent sound API that works outside Applets, is
simple, and does not overlap. This is what I did in VerCheck.  see
http://mindprod.com/applet/vercheck.html

2. pop up a dialog box.  Interrupts work flow.  User must dismiss it
first to get on with fixing a trivial error.

3. short sound.

4. non-modal dialog box.  Lets user continue working.  Disappears by
itself if not dismissed after a second or so.

5. reserved error box on the screen.  The problem here is it is out of
the line of sight.

6. icon for record that indicates if it ready for prime time.  You
hover over it to get a tooltip for why not.

What do you think the ideal way to handle error notification is?