Much of this sort of information was later reverse-engineered, and cross-browser support for basic operations is actually quite good. (Browsers still vary widely on the details.)

We’re happy to report that the good people at Google and Mozilla are moving towards adoption as well.

Products using the same version of Gecko have identical support for Web standards.

Firefox is at the forefront of cross-browser compatibility.

cross-browser development

I usually write example code that is for both Chrome and Firefox WebExtensions.