Future of the browser

Have browsers ever been 100% compatable with each other? I remember when Netscape and IE were close with HTML 1.0 but since then it has been a downhill road. So today you have 4 major browsers, Firefox, IE, Opera, and Safari all which are pretty much heading down different directions. The real battle will be Firefox and IE which represents the majority of usage. I was already hard enough to code html/css across these browsers and versions and now their foundations going forward will change and the thought of be compatable isn't part of their equation for desktop dominance. So with this challenge I think it's funny people talk about standards when the very browsers we use don't really care about supporting the common W3 web standards. In fact why bother with any of those standards and just makeup your own as Microsoft does since you already have customer lock-in. Just reading about Firefox 3 and it's truely a separate path than the others.