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

Dave,

> <https://addons.mozilla.org/en-GB/firefox/addon/http-status-code/>

Thanks. Alas, FF 52 thinks its corrupted somehow - probably too new (I saw 
some file extensions in that XPI that I do not recognise).

I will see if I can make sense of it, and if I can back-port it to a XUL 
style addon.

> You could also use a web proxy, like privoxy. I've used that
> to detect and change responses. But it's a lot of effort for
> what seems like a minor problem.

Indeed.  To be honest, I hoped it would perhaps be a simple about:config 
setting ...

Regards,
Rudy Wieser