Please bear with me, I don't know Linux well.
I have Knoppix 8.1 on usb. Firefox tells me it is critically out of date.
I ran apt-get update
I input to terminal:

knoppix@Microknoppix:~/Desktop$ sudo apt-get install firefox

and got:

The following packages have unmet dependencies: firefox : Depends: zlib1g (>= 1:1.2.11.dfsg) but 1:1.2.8.dfsg-5 is to be installed
E: Unable to correct problems, you have held broken packages.

Could anyone suggest what to do?