What do you do if you fall asleep while e.g. watching a movie? You drink some caffeine. Give your mac the same stuff to prevent it or the display from falling asleep if you don't want it to. You find Caffeine at http://lightheadsw.com/caffeine/ Happy bitnapping!
Please read the following before uploading
Do not upload anything which you do not own or are fully licensed to upload. The images should not contain any sexually explicit content, race hatred material or other offensive symbols or images. Remember: Abuse of the TV.com image system may result in you being banned from uploading images or from the entire site – so, play nice and respect the rules!