Want to prevent Ubuntu from going to sleep or turning black? Caffeine is a status bar application able to temporarily prevent the activation of both the screensaver and the “sleep” powersaving mode. With that you can enjoy movies without a break.

With caffeine, you can manually disable screensaver by one click:

Caffeine-applet

Or, set automatic activation for flash video, quake live, or other certain programs are running in its preferences window.

Caffeine-applet-preferences

To install the applet:

Caffeine is available in the ppa repository for Ubuntu 13.04 Raring, 12.10 Quantal, 12.04 Precise, 10.04 Lucid, and Linux Mint.

Hit Ctrl+Alt+T to open terminal, run command to add the ppa repository:

sudo add-apt-repository ppa:caffeine-developers/ppa

Then update:

sudo apt-get update

Install the applet:

sudo apt-get install caffeine

Once installed, start it from the Unity Dash.