The JSX specification is a XML-like syntax extension to ECMAScript.
ECMAScript 5/6 compatibility tables
DOM Parsing and Serialization Standard
Documentation for Opera Dragonfly
Opera extension adding support for the "Using CSS Selectors as Fragment Identifiers" specification: http://simonstl.com/articles/cssFragID.html. See also http://shauninman.com/archive/2011/07/25/cssfrag.
An Opera extension that shows a Chrome style popup statusbar when hovering links.