Starting with Firefox 63 (Nightly 2018-07-22), userContent.css can style standalone media documents like images, videos, and plugins. You can now get rid of the image background introduced in Firefox 11. You can also style Firefox's video player, if you're so inclined. Syntax is as follows:
Code: Select all
@-moz-document media-document(image) {
/* Style goes here */
}
@-moz-document media-document(video) {
/* Style goes here */
}
@-moz-document media-document(plugin) {
/* Style goes here */
}
Documentation is below, though it hasn't been updated yet. If you're looking for the technical details, the bug report is the place to go for now.
https://developer.mozilla.org/docs/Web/CSS/@document
Bug 1475511 - Extend @-moz-document syntax to let users style standalone images and videos