What is "good art"? The answer to that question depends on whom you ask, but if the artwork in question is scrawled on your wall, it's probably not gallery-worthy. But don't get bent out of shape if your little one decorated your wall in crayon, because you probably already have the perfect cleaner in your fridge. Just add some mayonnaise to a clean cloth, and dab it on the marks. Let it sit for five minutes, then wipe away the mayonnaise with a wet cloth. Dry the spot with a paper towel, and you're done.