Common:
all Suitable for all devices.
screen Computer screens and most handheld devices.
print Page-delimited mode for printing and print preview
Rare:
projection Projections/presentations, used by Opera 4+ fullscreen mode
aural Speech synthesizers, used by Firevox. Deprecated in CSS 2.1
speech Speech synthesizers, reserved.
tv Television displays, used by WebTV.
handheld Handheld devices, supported by Symbian.
Not used by any known agents:
braille Braille tactile feedback devices.
embossed Paged braille printers.
tty Fixed width character grid such as terminals.
