iMac Fading Light(right bottom corner) On Flat Panel

After seeing pictures of various peoples desk setups and workstations who have the flat panel iMac's, I noticed that the white little light that fades in and out is always on...however on my 20"iMac, the light only comes on when the computer is totally asleep...

Is it supposed to be on all the time or just during sleep mode? and if so, then how was the light on while the computer was in use, in the photos i saw??

I'm not certain about iMacs, but on my iBook it only comes on while it's asleep (and that's what's supposed to happen).

I have an IMAC and the light is on when the system is awake and fades in and out when it is in sleep mode.

bill

i have an iMac. The white light only comes on when it's sleeping.

The light on my iMac is on all the time and fades in off and on when asleep

can anyone explain why on some its like that and others its not, can you change it in system prefs or something?