The Collaborative International Dictionary of English v.0.48:

Acceptableness \Ac*cept"a*ble*ness\
   ([a^]k*s[e^]pt"[.a]*b'l*n[e^]s), n.
   The quality of being acceptable, or suitable to be favorably
   received; acceptability.
   [1913 Webster]

WordNet (r) 3.0 (2006):

acceptableness
    n 1: satisfactoriness by virtue of conforming to approved
         standards [syn: acceptability, acceptableness] [ant:
         unacceptability, unacceptableness]