How can I customize error messages.
I have my own scripts and I would like to customize some error pages so it can take some customized actions. - Is this possible? - Where to start from? - Where to grap the error HTML page and where to place my script? - If not, what are the alternatives? can I perfrom this via an extension? But the problem is that I want to display my error page before the original error page appears. I could not find a way to do such thing as "page-mod" changes URLs and I could not find the error pages URL that get displayed. When error occurs, the same URL stays as it is in the URL bar without error page link.
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There are built-in about pages like these (about:neterror):
- https://dxr.mozilla.org/mozilla-release/source/browser/base/content/aboutNetError.xhtml
- view-source:chrome://browser/content/aboutNetError.xhtml
I viewed the code. Neat but quite complex to be honest. Can you give a simple example please on how to specify the parameters for one error message, e.g. how to change the script. Where are these parameters read from? For example: "<title>&loadError.label;</title>", where is "loadError.label" is read from? how can I customize it?
The entities are defined in the files that you can see are linked.
- chrome://global/locale/netError.dtd
- https://dxr.mozilla.org/mozilla-release/source/dom/locales/en-US/chrome/netError.dtd
Customizing these pages is beyond the scope of this forum and best would be to ask advice at the Add-ons forum since you would need an extension. I do not know if this is possible with a WebExtension because otherwise your XUL based extension will stop working in Firefox 57+.