The problem is deeper than you imply. It's not just standards, at least not for everyone. I'm currently replacing a website that was developed several years a

The problem is deeper than you imply. It's not just standards, at least not for everyone. I'm currently replacing a website that was developed several years ago that does not work on Firefox. It is nothing special. It's your standard CRUD app. Not even an SPA. From what I can tell the tech they use is all at least 5 years old. They obviously never even checked to see if it worked in Firefox. It should work in Firefox. There is no excuse for it not to. If you are actually analyzing your featureset and saying "I could really use these new standards Firefox doesn't support", that's one thing. If you are just coding whatever and seeing it works in Chrome and calling it a day, you aren't coding to a standard, you are coding to whatever happens to work in Chrome.