This is absolutely not true. I wrote a simple flexbox layout in Firefox last year and it was majorly broken when I tried to test it on Chrome, since Firefox and

This is absolutely not true. I wrote a simple flexbox layout in Firefox last year and it was majorly broken when I tried to test it on Chrome, since Firefox and Chrome disagreed on how to compute "min-width" for inline images and other replaced content. In this case, my layout worked in Firefox, but Chrome was the browser that was following the CSS standard correctly, and my code was broken.