Important note: This plugin only applies to WordPress 2.1 – 2.1.2. The fix is included in the 2.1.3 source by default, and this plugin will no longer be needed.
Edit: Yes, I’ve just looked at 2.1.3 (which was just released) and this fix is in there. Do not use this plugin with 2.1.3 and up.
Lots of people like the new WordPress 2.1, but I noticed several complaints over on the WordPress support forums about the fact that the Firefox inline spell checking seems to not be working with the new editor.
I investigated, and it turns out to simply be one of the default settings of the version of TinyMCE that is being used. Even though it has a spell check button, some people prefer Firefox’s automatic spell checking. I can understand that, I use it all the time myself.
Fortunately, WordPress includes hooks for changing those TinyMCE settings, so it was a matter of a few minutes to create a plugin to deal with the issue.
Here’s a plugin to do just that. It’s simple to use, just upload to the plugins directory, then activate it in the Plugin panel. No configuration needed, it just turns the Firefox automatic spell checker back on in TinyMCE. Simple.