Screen Burn
What am I able to do about screen burn on my mac?
iMac, Mac OS X (10.6.5)
Are you saying that you have screen burn, or that you are worried about getting it?
Apple say this about LCD screen burn in:
http://support.apple.com/kb/HT2807
which includes suggestions for curing that effect.
Alternatively:
How to fix screen burn and/or stuck pixels on an LCD monitor:
JScreenFix