> If the symbols below are standard symbols, that is fine. Do you have
> pointer to a URL that describes these GUI standards?
> > empty black square - unselected, may be selected
> > black check or X in square - selected, may be unselected
> > empty grey square - unselected and stuck that way
> > grey square with grey check - selected and stuck that way
> > grey square with grey fill - N/A
They are common to Mac, Windows, Java, Mozilla, and
some of the many X toolkits/themes. Mostly, I think
everybody just tries to copy everybody else.
I do recall once seeing an image of all the normal
checkboxes together. I think there were about 20,
though the five I've described should pretty much
cover everything important.