What is the "chrome://" URL in Firefox error page?

Question

This is the Firefox error page when you're offline. If you look at the red marked area, you see the svg background and some scripts are loaded from chrome://browser/content/.... What does chrome do there?

Answer 1

Firefox uses the chrome:// protocol to access Mozilla's chrome system - user interface elements and other resources (chrome is not referring to Google Chrome here).

From developer.mozilla.org:

What is chrome

Chrome is the set of user interface elements of the application window that are outside the window's content area. Toolbars, menu bars, progress bars, and window title bars are all examples of elements that are typically part of the chrome.

Using a Chrome URL we can access those elements with a browser. For example, we can access the library menu with:
chrome://browser/content/places/places.xul
and the extensions menu with:
chrome://mozapps/content/extensions/extensions.xul
(URLs taken from http://kb.mozillazine.org/Chrome_URLs)

So, it seems that the chrome://browser/content/.. links are fetching Firefox resources needed to display the error page.