Function to prevent accidentally pressing the 'back' button

Dear admins

After multiple times having lost the whole text I've just written because I accidentally pressed the 'back button' key sequence on my keyboard (ctrl-left), I  kindly ask you to implement a javascript function which asks something like 'are you sure you want to leave this page?' in the "Bericht Editor" instead of just going back in the browser history.

Perhaps this article might give some indications:
http://jordanhollinger.com/2012/06/08/disable-the-back-button-using-html5


Rgds,
Dominik