Re: Retrieving a webpages shows a blank screen when a 4xx HTTP status is returned. Not helpfull.

Dave,

> If you're using an unsigned xpi you need
> xpinstall.signatures.required false

I know, but thats not the problem.  At least, not for a *temporary* loaded 
add-on.

Also, the *foreground* scripts work.  I tried the sample add-on as described 
here :

https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Your_first_WebExtension

, and that one works.

Its the *background* script(s) that won't.

... but I think I found the reason, and you probably wont believe it : I 
always, in about:config, disable JavaScript (I simply don't want to run 
active content from random websites).    But on a hunch I re-enabled it. 
And what do you know, the background script started to work (I saw some 
'console.log( )' messages appear in the the ctrl-shift-j 'Debugging 
Window').

I'm trying to figure out if its simply a bug, or a "that looks like a good 
idea" but they forgot to tell anyone about it ...

Either way, that it works that way greatly diminishes is use for me and 
thereby my urge to spend more time at looking how to write my own, new style 
add-ons. :-(

Regards,
Rudy Wieser