  Following hep-th/0001204 we discuss the computation of quantum corrections
near long IIB superstring configurations in AdS_5 x S^5 which are related to
the Wilson loop expectation values in the strong coupling expansion of the dual
n=4 SYM theory with large N. We use the Green-Schwarz description of
superstrings in curved R-R backgrounds and demonstrate that it is well-defined
and useful for developing perturbation theory near long string backgrounds.
