Go to Search Box : Shift+Alt+/
Facebook Help : Shift+Alt+0
Facebook Homepage : Shift+Alt+1
Facebook Timeline(Profile Page) : Shift+Alt+2
Facebook Friends : Shift+Alt+3
Inbox (Messages) : Shift+Alt+4
Notifications : Shift+Alt+5
Account Settings : Shift+Alt+6
Privacy Settings : Shift+Alt+7
Facebook About Page : Shift+Alt+8
Terms and Conditions : Shift+Alt+9
Comment on a story : Shift+Alt+c
Scroll between news feed : Shift+Alt+j,Shift+Alt+k
Like or unlike a specific story : Shift+Alt+l,L
Create New Message : Shift+Alt+m
It is very easy to remember Facebook Short cut keys on Firefox,as the short key starts with SHIFT+ALT Key.