Here are some handy Firefox shortcuts that I use all the time:
1) crtl-k — puts the cursor in the google search box.
2) crtl-l (that’s an L) — puts the cursor in the URL box.
3) ctrl-tab – switch tabs (forward)
4) ctrl-shift-tab — switch tabs (backwards)
5) ctrl-t — opens a new tab
6) ctrl-w — closes the current tab.
7) ctrl-shift-t — reopen previously closed tab in the current window. Press it again and open the previously closed tab, etc.