NOTICE: The Browser you're using may not be supported by HTerr. If you believe this to be in error, please check your browser's User Agent settings. Supports Pale Moon [25.0a1pre - 29.*] and Basilisk.
Welcome to the HTerr home page! This extension adds fallback error pages for websites that return HTTP errors with no content.
HTerr was just created in September of 2020, after Mozilla Firefox and Thunderbird had already converted to WebExtension standards, and was created specifically for Pale Moon.
HTerr is free for use or modification without limitation. However, it comes with no license, warranty, or guarantee of any kind. That being said, you can still ask any questions in the Comments section below, or contact me directly for assistance.
Comments
TannedSun
Mar 28, 7:13 PM
Could you use the original screenshot instead of a very small picture? It would help out a lot.
moonbat
Feb 9, 9:36 PM
Does this conflict with Fierr or is it different?
RealityRipple
Feb 9, 11:41 PM
It's entirely different; doesn't use the built in netError system, only its CSS. This extension literally just inserts body data into a 4xx or 5xx HTTP response using the 'http-on-examine-response' event of the Observer service. That means the error page you get from this extension is just a regular webpage according to the browser, and even the MIME type can't be altered, so if the empty HTTP error has a content-type of text/plain for whatever reason, the error has to be plain text instead of a webpage too, or it'll just show you the page's source code. It's more of a stop-gap measure for sites that send HTTP errors but no accompanying HTML data, so they don't display a blank page, rather than a true error handler.
HTerr
Pale Moon [25.0a1pre - 29.*] and 
Basilisk.
Browse Source Code
⚖️ Public Domain