Does this affect simple editing areas (like the ones on this site) or only rich text editors like webmail compose areas? The backspace key should only delete text in a basic form control, but rich text editors need to intercept it themselves, and it's possible that a change in Firefox has broken something used by their scripts.

To completely turn off the backspace/back mapping, see the solution in this thread: How can I disable 'backspace' key from navigating back a page?

It took me a little bit to figure out what you were describing and how to implement it, but I got it done.

Thanks

I hope I can remember that trick because I'm afraid I'll have to use it again some time soon as my Windows registry has gotten corrupted and I'll eventually have to reinstall all applications. I've been putting it off for a while now.

For rebuilding purposes, make sure to keep a backup of your personal Firefox settings folder (AKA Firefox profile folder). An easy way to access that folder is:

Help > Troubleshooting Information > "Show Folder" button

If you then navigate that window up a level, you can copy the currently active folder in its entirety. Useful for recovering bookmarks, history, and settings customizations.

You can bookmark the MozillaZine knowledge base article for future references.

• http://kb.mozillazine.org/browser.backspace_action

Note that there is also this extension:

• DisableBackspaceNavigation: addons.mozilla.org/firefox/addon/disablebackspacenavigation/