Nobody writes to the standard, because no browser is strict about only accepting standards-compliant code. Personal experience—there are a raft of minor differ

Nobody writes to the standard, because no browser is strict about only accepting standards-compliant code. Personal experience—there are a raft of minor differences between Chrome and Firefox, just to pick two. For example, they parse SVG paths differently. The exact behavior of <audio> tags when starting and stopping them used to be different (don’t know if it’s fixed). There are a bunch of other minor things. I have many times discovered that my app doesn’t work in Firefox if I’ve been developing in Chrome, or vice versa. If you write a lot of weird code, you can easily end up with broken features or a blank app and stack trace after switching browsers. Of course, 95% of the time it will work fine.