removing acrylic paint off of walls?

[soo-jie.livejournal.com]

i'm sorry if this has been asked before, but is there a way to remove acrylic paints from walls? i don't think i should paint over it with another color, since the acrylic is opaque and can show through. i made quite a lot of mistakes by dabbing all over my walls, and it's kinda embarrassing when people come over and see it, haha. ^^;; is there also a way to remove permanent marker as well? 

please help and much thanks! ^____^