Why can't I add this class online?

When you add a class online, the selected course may return an error message when you submit the CRN. It is important to read what type of error you have encountered on the far right hand side of the screen. Registration errors include closed courses, waitlisted courses, prerequisite restrictions, co-requisite restrictions, class level restrictions, college restrictions, major restrictions, and time conflicts. If any of these errors occur, you must use a Special Registration Form to add the course and have the appropriate restriction override box stamped by the department or signed by the instructor.