The effect of imperfections on surface critical properties is studied for
Ising models with nearest-neighbour ferromagnetic couplings on simple cubic
lattices. In particular, results of Monte Carlo simulations for flat, perfect
surfaces are compared to those for flat surfaces with random, 'weak' or
'strong', interactions between neighbouring spins in the surface layer, and for
surfaces with steps of monoatomic height. Surface critical exponents at the
ordinary transition, in particular $\beta_1 = 0.80 \pm 0.01$, are found to be
robust against these perturbations.Comment: 7 pages, 13 figures, submitted to European Physical Journal