This volume attempts to connect early error research with current orthographic systematic findings and to illuminate some methods for diagnosing spelling performance in this context, while also considering the aspects of specific conditioning factors in the acquisition of written language. It would be desirable for future research on written language and specifically on orthographic acquisition to regard errors as elements of the phenomenon level: errors as indicators and aids that can help reconstruct the system of internal rules underlying a particular learner's spelling competence at a given time in a comprehensive overview.