chrome.manifest content directive problem

[BeginnerDeveloper]

Hello, as my nickname says I'm a beginner in all of this.
I received a task to create an extension for Thunderbird but I can't even begin work on it because it does not work at all.
I tried (I know it says it is out-dated but I have no other source of information):
https://developer.mozilla.org/en-US/Add ... _extension
and
https://developer.mozilla.org/en-US/doc ... bar_button .
Every time pretty much the same error appears:
JS Error Message Box(or whatever the name of it is) says: Ignoring unrecognized chrome manifest directive 'content'. 1 chrome.manifest:1
next message: No chrome package registered for chrome://myfirstext/content/myhelloworld.xul .
I will be very grateful if you guys would help me with this one.

[lithopsian]

Your chrome.manifest file is not in a valid format. It might help to post your chrome.manifest file.

[BeginnerDeveloper]

Your chrome.manifest file is not in a valid format. It might help to post your chrome.manifest file.

I created this file with windows' notepad. I set encoding to UTF-8 and saved it as any file type, just put "chrome.manifest" as the name of file.
Then when I read your post I tried to create .manifest file with VS2015 and just replace the code. It did not help either.
This what I copied from tutorial and put in this file:
content myfirstext content/
overlay chrome://messenger/content/messenger.xul chrome://myfirstext/content/myhelloworld.xul

I've no idea why it does not work.

[morat]

I got a simple commandline extension working here. No problems.

http://forums.mozillazine.org/viewtopic ... &t=3021875

I created the files with Microsoft Notepad. I saved the files as text documents.

Thunderbird 52.2.1
Windows 7 SP1 32-bit

P.S.

Perhaps, there is an odd character in the chrome.manifest file.

Unicode code converter (paste text in the green box and convert)
http://r12a.github.io/apps/conversion/

Edit:

Sorry, I only tested ANSI not UTF-8 with Microsoft Notepad.

[lithopsian]

There is a known problem with UTF-8 files having a BOM, which is exactly what notepad does. So don't do that. notepad++ can save files without a BOM, which should work. Or just don't save as UTF-8.

[BeginnerDeveloper]

There is a known problem with UTF-8 files having a BOM, which is exactly what notepad does. So don't do that. notepad++ can save files without a BOM, which should work. Or just don't save as UTF-8.

Thank you very much! The solution was so simple!

I got a simple commandline extension working here. No problems.

http://forums.mozillazine.org/viewtopic ... &t=3021875

I created the files with Microsoft Notepad. I saved the files as text documents.

Thunderbird 52.2.1
Windows 7 SP1 32-bit

P.S.

Perhaps, there is an odd character in the chrome.manifest file.

Unicode code converter (paste text in the green box and convert)
http://r12a.github.io/apps/conversion/

Thank you! I'll check it out.