Restarting iMacs
If the power light shown below is GREEN, just slide the mouse or tap a key. The iMac will jump to attention. If the power light is slowly PULSING YELLOW, tap the mouse button; the iMac is sleeping and will wake up in about 10 seconds.
NEVER TOUCH THE POWER LIGHT unless it is dark for 5 seconds.
You should also never touch the power light shown below:
If the iMac is really frozen (wait at least one minute to see) you can RESTART it by pressing the restart button shown below. It's on the right side of the iMac and has a black triangle on it:
