On Macbook Pro, F5 and F6 seems to be the "keyboard illumination keys".
However, the keyboard's illumination doesn't seem to change at all after pressing those keys.
Also, I noticed a small "no entry" sign whenever I hit those keys, how do we fix these problems?
The laptop makes note of ambient lighting and disables keyboard backlight when it's not dark. This is similar to the automatic display brightness system. Both are there to save power.
Your keyboard backlight should work in a dark room or if you cover your iSight camera so the laptop thinks it's dark.
