Check to see if there is an updated version of the add-on you were trying to use.

Check within Firefox menus. Look for Add-Ons.

Hello nostalgia, go to about:config, find devtools.scratchpad.enabled and double-click on it to make it FALSE, exit firefox and restart it.

thank you

That doesn't work.

Where (How) are you opening the JS files?

See also:

• http://kb.mozillazine.org/view_source.editor.external
• http://kb.mozillazine.org/view_source.editor.path

E. g. CTRL+SHIFT+A -> User Scripts -> RMC -> Edit

Is this with the Scriptish extension or GreaseMonkey?

You should be able to change which editor to use in the Options/Preferences via the about:addons page or via its menu entry.