回複：請問F1身份是否可以讀一門網絡在線課程，其它的在學校讀？

For circumstances, an F-1 student may take courses less than FT
http://blog.wenxuecity.com/blogview.php?date=200804&postID=4128#F1

However, if you intend to take online course which is not offered by the school on your I-20, it's ok.