It's not about vendor prefixes; MS IE implements a very old version of the CSS Grid Spec. But I guess MS will update the implementation now that CSS Grid is Can

It's not about vendor prefixes; MS IE implements a very old version of the CSS Grid Spec. But I guess MS will update the implementation now that CSS Grid is Candidate Recomendation. Actually, Rossen Atanassov (Microsoft) is one of the current authors of the spec.