In some circumstances the debugger just doesn't kick in. There are
still some steps that you can take though. The first thing that I
would do is add an alert statement to check that the JS code is indeed
running in Firefox as expected ... you would be surprised how often
code is not running due to some quirk somewhere else. If the code is
running and the debugger statement is not triggering the debugger you
will have to just log your variable to the console. This can be very
useful because you can dump JS objects in the way that Firebug does.
The syntax is simply console.dir(somevar).