1. On the menu bar, click on the Firefox menu and select Preferences...
2. Select the Content panel.
3. Under Fonts & Colors, click the Advanced... button
4. Under Monospace, select Courier New on the dropdown menu

For more information, see Change the fonts and colors websites use.

That's not what I want. I want Courier, not Courier New (which, it turns out, it was already set to). Using your instructions I tried to set it to Courier, but after clicking "OK" and so on, it goes back to Courier New automatically.

Could you try resetting your user preferences and see if it will solve the problem?

1. On the menu bar, click the Help menu and select Restart with Add-ons Disabled... Firefox will start up with the Firefox Safe Mode dialog.
2. Put a check mark by Reset all user preferences to Firefox defaults.
3. Click Make Changes and Restart.

Unfortunately that didn't help either.

We’ve established, I think, that this is a problem with Firefox rather than any specific website. Could you reinstall it again by going to getfirefox.com?

Okay, after a lengthy process of trying stuff...

I tried reinstalling the update over the rest - didn't work. I tried uninstalling Firefox (while leaving preferences/etc intact), then reinstalling entirely - didn't work. I tried a complete uninstall (removing preferences/add-ons/etc), then reinstalling - still didn't work.

Thank you very much for your attempts to help, but at this point I have to admit I'm kind of resigned to the change.

Okay, I fixed it, but it turns out I had to downgrade back to a version of Firefox 9 to get Courier to display the way I liked. Still, thank you again for your efforts, bram!

You’re welcome, and sorry that I couldn’t resolve your problem!

Just curious: back in Firefox 10, could you change Courier New to any typeface you want, or does the font menu only refused to work with Courier?

It might be a new bug that you (or I) could file on Bugzilla, if you like to help.

I could change Courier New to other typefaces, just not to Courier for some reason. Whenever I tried to do that (before or after reinstalling Firefox 10.0), it would automatically change back to Courier New.

I once had the same problem on a more generalized level (following a Windows update which I had to system restore to fix), but this was localized entirely to Firefox.

I'm entirely unfamiliar with Bugzilla, though.

The Courier font that you have may no be compatible anymore with Firefox 10 if you can't select it.

You can do a font test to see if you can identify corrupted or not working font(s).

• http://browserspy.dk/fonts-flash.php?detail=1

Hmm. Did that test and it doesn't even list Courier for me, just Courier New and forms of that.

If they don't show up in the list of the default fonts and also are not identified by the Flash plugin on the test page then they are most likely no longer compatible.

It showed up on the list on Firefox, but the plugin on the test page didn't detect it.

I’m going to try changing Courier New to Courier on my Windows (admittedly XP) machine tomorrow. If it doesn’t work, then it’s probably a bug.

Cor-el, do you have Windows 7, and if so, could you reproduce this problem?

No, I'm on Linux, so can't test it on Windows.

I've tested it in Firefox 10 and both Courier and Courier New show correctly.

• fontinfo: https://addons.mozilla.org/firefox/addon/fontinfo/