(Work with Araceli Bonifant.) The usual theory of orbifolds studies the quotient space of a smooth manifold under a proper group action. However, even when the action is not proper, a weak form of orbifold theory is still possible. The talk will apply these ideas to the action of the group of automorphisms of the projective plane ${\mathbb P}^2$ on a space of curves of degree $n$ in ${\mathbb P}^2$.