  It is well known that for every $f\in C^m$ there exists a polynomial $p_n$
such that $p^{(k)}_n\rightarrow f^{(k)}$, $k=0,\ldots,m$. Here we prove such a
result for fractional (non-integer) derivatives. Moreover, a numerical method
is proposed for fractional differential equations. The convergence rate and
stability of the proposed method are obtained. Illustrative examples are
discussed.
