alternatives:

* alert if any form filled by user wasn't submitted (in case site doesn't do that already)

* let 99% of user who don't know what they did (they are in minority compared to number of times backspace is pressed to actually navigate back) retype their form if they don't navigate forward (which recovers their input, or should)

* add a third hand to human race so it doesn't take all the hands to navigate back from keyboard

* lure lenovo to restore the back / forward keys on thinkpads and make that implemented on most keyboards