"Mozilla supports the types: "text/javascript", "text/ecmascript", "application/javascript", "application/ecmascript", and "application/x-javascript", and supports a "version" parameter on all of those types, which is in the range 1.0 to 1.8 (exact string match, not numeric match), and also an "e4x" parameter taking values "0" or "1" (for example, "text/javascript; version=1.7"). Which version is specified turns on/off a number of language features that may be backwards-incompatible."

(also note the comments about video's @autobuffer param)

Highly experimental Mozilla builds. Henri Sivonen's HTML 5 work is in here.

"Crowbar is a web scraping environment based on the use of a server-side headless mozilla-based browser. Its purpose is to allow running javascript scrapers against a DOM to automate web sites scraping but avoiding all the syntax normalization issues."

How Firefox 3.1 implements HTML 5's <audio> element.

Or why IE's handling of <object> is a pain in the ass.

thoughtful analysis of "almost standards mode" and IE 8's versioning switch