From Mozilla Support (emphasis mine):
Several times over the last couple weeks, I type up a very well thought out response on Facebook in political conversations with friends. An hour or two into my work, I hit backspace with the intent of editing what I wrote (maybe after I scrolled or something, so maybe I unintentionally took the edit window out of focus). The navigator takes me back a page and I lose my two hours of work. Infuriating! Shortcuts with the ability to wipe out two hours of works should be disable-able.
I feel your pain, buddy.
Shortcuts with the ability to wipe out two hours of work should not be included, period.
Who thought it was a good idea to use backspace (which deletes text) as a navigation button?
The problem is not just that the backspace button is dangerously overloaded. It’s that going forward again does not restore your work! There is no undo for this stupid feature.
By the way, to disable this in Firefox, enter
about:config into the address bar, search for browser.backspace_action, double-click on the setting, and enter 2 in the modal dialog. Clear as mud.
I’ve asked Mozilla to disable backspace as a navigation button by default. I know it’s breaking with convention, but this convention is broken.