Good advice but what kind of screen is it? If it is an LCD,,,do not use anything on it but what someone like Circuit City or Best Buy recommends. Anything the is not specific will ruin the plastic on the screen for ever. If it is a regular CRT monitor with a glass screen , any glass cleaner will clean the ink off or Rubbing alcohol.
I used Rx eyeglass cleaner. It states that it is safe for coated lens,soooo, thought it would be safe for computer screen. It was, and it worked. I used the eyeglass cleaning cloth that comes with cleaning solution. Will now be more vigilant keeping 2 year old great-grand out of computer room.
Clorox liquid bleach and detergent is a good way to remove ink marks from your computer. You can also use alcohol for stain removal. There are also liquid cleaners for hardware available in the market and that can also remove stains from your hardware.