In this study, we will insist on some characteristics of written products belonging to the students of French philology. We will give some examples concerning different types of errors, but firstly, it seems that we need to study the notion of norm, because norms are different from each other and the notion of false represents various types of errors or missing points. Therefore, we are faced with this fact: the distinction between false and correct depends some time on which norm is chosen. Once the notion of norm is studied, we will show some examples of errors that concern, by nature, different domains like phonology, morphology, syntax and lexique.