These are top 10 shortcuts of Fire fox which can be said as must known shortcuts.
Ctrl + T and middle-click
If you want to open new tab than this shortcut or mouse middle button will open a new tab for you.
also you can open any link in new tab by same method.
Ctrl + Shift + T
If you close a tab accidentally use this command to undo changes. If you type this command multiple times it will restore previous tabs in closing order.
Ctrl + , Ctrl – , and Ctrl + 0
if you want to increase page yext size use Ctrl +, If you want to decrease page font size use Ctrl -, If you want to go back o default page font size use Ctrl + 0.
If you want to navigate to address bar quickly, use F6 key.
Ctrl + J
you download a thing and now u need to open download manager??? just use this short cut key to open download manager
Ctrl + F or /
If you want to find any text in a webpage this shorcut key will open a find box for you, type your desired word and press enter or / and this will search the word for you.
Ctrl + D
Open bookmark window for page currently viewing.
Ctrl + W
If you want to close the current tab tou are using this key will help you in closing current tab.
Ctrl + Tab or Ctrl + Shift + Tab
If you want to move between open tab, use these keys to navigate.
If you want to see toolbar just enable full screen mode by pressing f11.