It's happened to me several times now that I press backspace, thinking that I am in a dialog box, while I am not. This causes my browser to jump backwards a page, rendering all I have done since the last time I saved null and void.
While this is certainly something that can be tackled through frequent saving, it's simply annoying to lose any work at all, especially through pressing such an oft-used key.
I'd like to suggest an "are you sure you want to leave" message when trying to leave the page when changes have been made, with the option to back out, to tackle this problem. It'd really save me a lot of headaches when trying to edit trials.