to Chessmaster1000: Castling is not allowed then, because the Rook e8 is threatening. Be aware that the King is always moving *ON* the board because castling is an iterated King's move, where the involved Rook is invisible. You can compare that situation to an e.p. capture move, where a Pawn is allowed to answer each of the iterated double Pawn steps. Because check would be applicatable to each of the King's iterated steps during castling, it would be allowed to capture the King. Thus castling is forbidden there, even when the threatened square is filled with the involved Rook.