How to close Apps in Windows 8?
"There are 3 ways you can close metro apps in the new Windows 8:
1. If you have a touch screen tablet or laptop, touch your finger on the top of the screen and drag it all the way to the bottom. It will minimize and move the app from your way.
2. If you don't have a touch screen but you use a mouse, do the same with the mouse. Point your mouse on the top of the screen and drag it all the way down. When you point the mouse to the top of the screen, you can see the cursor is changing.
3. Press ALT key + F4. This will still work just like the traditional Windows programs.
4. The killer option: use ALT+CTRL+DEL and kill the app using the task manager.
Also, some sources have indicated that the ALT + F4 option may not reliably work to close metro applications in Windows 8. However, so far it works fine, even though Microsoft may change this later releases.
Note that the traditional Windows applications will continue to have close and minimize buttons. You can close them the way you are familiar with."