Question

I want to make it so my rules apply by default to all the sites/pages except the ones I list.

Sort of like an opposite of @document domain(mozilla.org)

https://developer.mozilla.org/en-US/docs/CSS/@document

edit:follow-up regex

Answer 1

There isn’t an easy way to do this currently, as noted in this CSS Conditional Rules draft with a link to a Mozilla bug report:

This syntax doesn’t offer any ability to do negations, which has been requested in Mozilla bug 349813. Use cases that people have wanted negations for include:

• User style sheets that want a particular rule in general, but know that that rule does more harm than good on specific sites.

• Authors who have a rule that they want to apply to most of their pages, but wish to make a few exceptions for.

Hopefully, they’ll propose and implement such a feature soon.

In the meantime, you may be able to achieve something with regexp() which accepts a JavaScript regex with certain flags — details are included in the spec — but I can’t make any guarantees.