We've all been there. Things are slow at work and you find yourself somewhere you shouldn't be, like playing a game of online Scrabble or watching some painfully awful rendition of the national anthem on YouTube. Without warning, here comes the boss and he or she seems to be approaching at the speed of light. In a state of panic, you fumble with your mouse and keyboard in an attempt to close your browser before its too late. No such luck, as the six deadly words fill the air in your cubicle: "What is that on your screen?".

Don't let this happen to you! These shortcuts can help you hide or shut down your browser lickety-split. Just be sure that you do not have any important work open in your browser if you intend to quit the application.
Please note that on Macintosh (OS X), using Hide is noticeably faster than using Quit.

Macintosh (OS X)

Safari

Hide all browser windows (also hides Safari windows from your dock): Command(Apple) + H
Quit Safari (exits the browser application completely): Command(Apple) + Q
Firefox

Hide all browser windows (also hides Firefox windows from your dock): Command(Apple) + H
Quit Firefox (exits the browser application completely): Command(Apple) + Q
Internet Explorer

Hide all browser windows (also hides Internet Explorer windows from your dock): Command(Apple) + H
Quit IE (exits the browser application completely): Command(Apple) + Q

Windows

Internet Explorer

Minimize all windows (this will minimize all open windows to your Windows taskbar): Windows Key + M
Quit IE (this will only quit the active instance of IE; if you have other windows open, you will need to repeat this shortcut for them): ALT + F4
Firefox

Minimize all windows (this will minimize all open windows to your Windows taskbar): Windows Key + M
Quit Firefox (this will only quit the active instance of Firefox; if you have other windows open, you will need to repeat this shortcut for them): ALT + F4
Opera

Minimize all windows (this will minimize all open windows to your Windows taskbar): Windows Key + M
Quit Opera (this will only quit the active instance of Opera; if you have other windows open, you will need to repeat this shortcut for them): ALT + F4