Blue ink mark on my LCD monitor

courtesy of one of my daughter's little friends. How do I safely get it off?

 

Use a solution of diluted isopropyl alcohol, no more than a 50% solution. Usually the rubbing alcohol you buy at a drugstore that is either 90% or 98% pure but 98% is pretty hard to get (you don't need it anyway). I mix 1 part water and 1 part 90% isopropyl alcohol, which works out to... um.. something just under a 50% solution.
Be absolutely sure to use a very VERY soft cloth. I use a piece of soft flannel. Do NOT use paper towels or anything more abrasive than an old worn out cotton Tshirt. Absolutely do NOT use windex or anything with ammonia in it, it can etch the screen surface and can cause the plastic to go cloudy. You don't want that to happen!

OR you can go to staples(or ??) and buy it in a bottle for about 5 bucks or so.