But does it mean the 15% is non-standard or just not implemented at all? If it’s not implemented then all of the implementation is 100% standard compliant and if everyone stopped relying on the 15% part then developing for Firefox should make it compatible for rest of the browsers.
If they develop for only Firefix it will work with all browsers because Firefox is standards compatible.
Not really, unfortunately. Firefox has only like 85% of the spec implemented, iirc. It is the browser I develop in most, personally, though, fwiw.
But does it mean the 15% is non-standard or just not implemented at all? If it’s not implemented then all of the implementation is 100% standard compliant and if everyone stopped relying on the 15% part then developing for Firefox should make it compatible for rest of the browsers.