Keyconfig extension
Description of Keyconfig
The extension Keyconfig allows you to configure keyboard shortcuts. It works with Firefox, Thunderbird and (probably) with the Mozilla Suite.
Shortcuts defined via a key can be changed. For more details read this: http://www.extensionsmirror.nl/index.php?showtopic=254
Miscellaneous
To set a shortcut to Ctrl + Space bar type a space " " (without the quotation marks) in the right box (for the shortcut).
Custom Keys
You can add preferences for custom keys to to the file prefs.js in your profile to get the described results. All instances of Firefox/Thunderbird must be closed before editing this file. After editing start FF/TB and open the Keyconfig window to add your keyboard shortcut.
Attention: Don't add this preferences to your user.js, because they would be applied again with the next start of FF/TB and therefore the assigned keyboard shortcuts would be overwritten (deleted).
Template
user_pref("keyconfig.main.xxx_key__NAME", "!][][][FUNCTION");