It's the same meaning, but some people/dictionnaries recommend to say "ce n'est pas ma faute" because it seems that "ce n'est pas de ma faute" appeared more recently. You can say "à qui la faute ?" as well as "de qui est-ce la faute ?", "c'est ta faute !", "c'est de ta faute !". As for me, I recommend you to use "c'est de ma faute" because "c'est ma faute" sounds quite childish. But it's a personal opinion :)

To my mind "c'est pas ma faute" or "c'est ma faute" put a stress on "ma" and is more exclamative "c'est pas MA faute!!" "C'est TA faute!!!" Then "C'est pas de ma faute" or "c'est de ma faute" is less direct, "It's (not) because of you if something happen" exemple: "C'est de ma faute si tu es en retard = You're late because of me..." But you can use both of them no one will pay attention^^

It is all the way your mistake ;).In fact you can use both!