In quite a number of cases students hit the Back button or Backspace key incidentally while taking final semester quizzes. They are taken to a previous page, we tell them to go forward one page to get back to the quiz, after which most of their answers are preserved and can be submitted. The essay questions are different in that they use the HTML editor, therefore going forward to the quiz page again loads the editor again and all the user has written so far in the essay question textarea is lost.

Two features could perhaps be added to help prevent this:
B. When in the essay question field, hitting Back button/Backspace key would trigger an alert: Do you really want to abandon this question and lose everything you have written so far? (similar, e.g., to Gmail alert when composing a new email and trying to get one page back);
B. An autosave mechanism would save the content typed into the essay questions fields, so that going back and forward would preserve the input.

Feature A seems easier to implement, B would be more comfortable.