I have had this problem a couple of times today, and on two separate computers. I have been typing a reply to someone, and do a few clicks inside the text box while editing, and then hit the delete/backspace button (I'm on a Mac) and it takes me to the last page rather than deleting the text I was editing. When I hit forward, my whole reply is gone.
As you can imagine, this is rather infuriating, especially when time is short, or it was a lengthy reply. Could you either implement a method of saving the text in the text box when "back" is pushed, or ensure that the cursor remains inside the text box?
Which OS, browser type, and browser version number are you using?
Google Chrome has this issue; either use another browser or click "Switch to plain text editor" underneath the text box and that will stop it.
Mac OS and Chrome here.
Thanks for that Stephanie. This issue has almost single handedly led me to jump off a highway overpass! So annoying.