Earth Hour 2013

Google
Earth Hour has also received free publicity from the Google corporation. From 12:00 a.m. on March 29, 2008 until the end of Earth Hour, the Google homepage in the United States, Colombia, Canada, Denmark, Ireland and the UK was turned to a black background. Their tagline is, "We've turned the lights out. Now it's your turn - Earth Hour." However, Google stated that for 2009 they would not turn the page black again due to the confusion it caused many users. A common misconception is that having a black background on a web page reduces the power consumption of monitors; LCD monitors use a constant amount of power regardless of which colors are shown. This is not the case for Organic LED monitors, though they are not currently in popular use.
Also YouTube has light switches on their videos and comments.