  We consider the ${\mathbb Z}^n$-graded algebra of global sections of line
bundles generated by the standard line bundles $L_1,\ldots,L_n$ on
$\bar{M}_{0,n}$. We find a simple presentation of this algebra by generators
and quadratic relations. As an application we prove that the moduli space
$\bar{M}_{0,n}[\psi]$ of $\psi$-stable curves of genus $0$ is Cohen-Macaulay
and normal, and the natural map $\bar{M}_{0,n}\to \bar{M}_{0,n}[\psi]$ is a
rational resolution.
