When I tried changing my password on FireFox, I keep getting error message "Please type 6 characters in the image.".
As this works as expected on Opera and Internet Explorer, I think there's a problem with FireFox. So, I check Error Console and read its error message.
The problem is FireFox complaints about getting directly value of input ID.
e.g <input type="text" id="txt" name="txt" value="some text" />
However, this works: alert(document.getElementById('txt').value);
So, I corrected the script, and the problem has no reason to exist :D
Thanks Daphna for informing me this problem :)