This message is generated when a face specification in the value of the FaceGrids option is not valid.
If the value of the FaceGrids option is a list, each element in the list should specify a face on which to draw grid lines, and (optionally) the position and style of individual grid lines.
The face specification in the value of the FaceGrids option is expected to be {-1,0,0}, {1,0,0}, {0,-1,0}, {0,1,0}, {0,0,-1}, or {0,0,1}.
Off[message] switches off the message; On[message] switches it on. For example: Off[FaceGrids::gface].