Backspace
Unless disabled by the teacher, you can use the Backspace key to correct mistakes in a word. However, you must do this before hitting Space. Once you press Space you can no longer make changes to a word. If there is a mistake, the word is marked incorrect.

The reason for not letting you go back in the text to correct all mistakes is that we want you to concentrate on typing accurately and go forward without interrupting your typing. Also, learning to rely on the Backspace key can prevent you from typing your best later on.