pressing back key outside an text input field or pressing the ‘go backwards one page’ button during study results in losing unsaved progress
the progress should be saved or the user should be prompted if they really want to return to the last page
Pressing the back key in firefox outside an text input field results and the browser interpreting this as the user wanting to return to the previous webpage. other websites like gmail, interrupt the process of returning to the previous webpage and instead ask the user if that really was their intention.
in webapps it is also possible to create virtual pages, so the webapp itself manages requests of going back or forewards and this could also be used to avoid losing data