Yes, the effects stack. What happens is that Magical Resistance is checked, then Elemental Resistance, then Magic Absorb. Note that while both Magical Resist and Elemental Resist can reduce damage, Magic Absorb is all-or-nothing -- either it absorbs or it doesn't. And the spell damage going through Magic Resist and Elemental Resist first means it'll Absorb less with more Resist (which isn't your problem if you only care IF it absorbs, not how much it absorbs and converts into magicka).