Question

That would be helpful except that it does not open the page in the external page source editor that I have set in config. It still opens it in the default Firefox page source viewer which is lame and useless for editing!

You can first open the source code in a Firefox tab with the view-source: protocol and then use View Page Source (Ctrl+U) to open the source in the external editor.

That does not work, at least on my installation. It merely opens the source page in a second Firefox source viewer window and not in an external editor window. I have the path to my Notepad++ escaped as suggested elsewhere but it does not get called or opened.

(fixed for Southerner as per: [/questions/939775#answer-406824])

As Cor-el said, it is working now.

that worked. No changes that I made in about:config seemed to make much difference but editing prefs.js directly as you suggested (for 64 bit Windows 7):

user_pref("view_source.editor.path", "C:\\\\Program Files (x86)\\\\Notepad++\\\\Notepad++.exe");

The config file shows the path to Notepad++ as being identical to what I had already entered! That entry is and was: C:\\Program Files (x86)\\Notepad++\\Notepad++.exe

It is ironic that entering it in Prefs.js made it work but putting it in via the about:config page did not.  Of course in prefs.js there are two back slashes for every one shown above.

Oh well, at least now it works.

Thank you.