YouTube Lights Out Script for Firefox and Chrome

Want to turn the lights out for watching YouTube videos? You would like the Script I recommend today.
After your browser installed the YouTube "Lights Out" script and then restarted, you will see a bulb icon next to Subscribe.

 When you click it, your browser's background would be a little black, click twice, totally black.


 If you use opera, you can try this script(this script could works on firefox & chrome too).
For the installation tips, you can view the YouTube Download Script post.