cross browser detection of modifier keys

[Mutley2003]

I want to detect which keys are held down when an onmousedown or ondblclick event is handled.

The example at
[webreference.com...]
does not work for Firefox ..

can anyone explain why and what I should do to make this truly cross browser?

thanks

[Bernard Marx]

That tutorial is so out-of-date it smells.

See: [quirksmode.org...]
(The section on modifier keys is near the bottom)

[Mutley2003]

thankyou .. quirksmode is very cool