Question

Chrome works just fine, and my Greasemonkey script, if copy/pasted into Firefox’s Firebug, works just fine on these pages but I can’t seem to get it automatically execute.

Download & install the script: http://sente.cc/js/testing_greasemonkey.user.js

and then go to https://i.stack.imgur.com/MK8ve.jpg (observe simple alert) and https://i.stack.imgur.com/q0tbI.jpg (observe no alert)

the script:

// ==UserScript==
// @name          Testing Greasemonkey
// @namespace     stuartpowers
// @description   Testing Greasemonkey
// @author        Stuart Powers
// @homepage      http://sente.cc/
// @include       http://i.imgur.com/*
// @include       http://imgur.com/*
// ==/UserScript==


// load https://i.stack.imgur.com/MK8ve.jpg (works)
// load https://i.stack.imgur.com/q0tbI.jpg (doesn't work)

(function () {
    alert("worked");
})()

Answer 1

No, Greasemonkey requires an explicit DOM to fire and act upon. It cannot run on Chrome-generated¹ pseudo-DOM².

If you want to act on these kind of “pages”, you’ll have to write a Firefox extension (add-on). (Note that userscripts in Google-Chrome are converted into mini extensions.)

Here are some add-on resources, I’ve found helpful:

• Mozilla extensions home page
• Add-on Builder
• 10 Things They Never Tell You In Firefox Extension School
• Developing Firefox Extensions – Paper

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¹ Here, “Chrome” refers to the privileged DOM that makes up the Firefox’s UI.
² With select exceptions.