A special KeySym value of NoSymbol should be used to fill in unused elements for individual KeyCodes. It is legal for NoSymbol to appear in nontrailing positions of the effective list for a KeyCode. There is no requirement that the X server interpret this mapping. It is merely stored for reading and writing by clients. The server failed to allocate the requested source or server memory.
Some numeric value falls outside the range of values accepted by the request.
Unless a specific range is specified for an argument, the full range defined by the argument's type is accepted. Any argument defined as a set of alternatives can generate this error.