The study of student error, important across many fields of educational research, has begun to attract interest in the field of e-learning, particularly in relation to usability. However, it remains unclear when errors should be avoided (as usability failures) or embraced (as learning opportunities). Many domains have benefited from taxonomies of error; a taxonomy of e-learning error would help guide much-needed empirical inquiry from scholars. Drawing on work from several disciplines, this article proposes a preliminary taxonomy of three categories: learning task mistakes, general support mistakes, and technology support mistakes. Suggestions are made for the taxonomy's use and validation. (Contains 2 tables and 1 figure.)