Backspace produces a browser history back
It has happened to me a couple of times that I press backspace during an excersive and the browser performs a "history back", changing the page to the skill page, making me loose all progress in the excersive.
I don't know under what circustances this happens nor could I reproduce it on porpuse, I just wanted to report it nonetheless.
Chrome. Usually web pages behave like you say; unless typing in a "textarea" backspace calls "history.back()". Web developers usually need to manually unbind the keyevent. Given that I couldn't reproduce that, my best guess is that developers did unbind it, but unbinding randomly fails in my computer (and apparently always in yours). Browsers can be capricious. I've installed BackStop though, because I've always find that annoying (web pages used to be static, but now you write a lot and accidental backs are annoying), thanks.