How can you remove a skin mark?

It is entierly dependant on the nature of the mark. A dirt mark or stain will wear of in time naturally; a skin blemish or tatto must either be covered with concealing make up or removed surgically - very occasionally they will slowly disappear over time (blemishes that is). The best approach is to learn to live with the body that nature gave you - it is what makes you, well, you and truly unique. There is no need to alter yourself to fit a standard model - you are fine as you are, skin marks and all!