We prove some generic properties for Cr, r=1,2,...,∞,
area-preserving diffeomorphism on compact surfaces. The main result is that the
union of the stable (or unstable) manifolds of hyperbolic periodic points are
dense in the surface. This extends the result of Franks and Le Calvez
\cite{FL03} on S2 to general surfaces. The proof uses the theory of prime
ends and Lefschetz fixed point theorem