Opera issued a feature-incomplete alpha version of its desktop browser today. The two aspects introduced in 11.00 are the revised JavaScript engine and Extensions. More features will follow - sometimes these are introduced late in the release cycle.

Opera releases are always worth a look. It's the testing ground for new features - and a preview of what Mozilla's Firefox and Chrome will implement in about three years' time.

Extensions are browser add-ons made using Opera application programming interfaces (APIs) and web standards like HTML5 and JavaScript. Extensions allow users to make their web browser their own by adding features and functionality directly into the browser itself, rather than as standalone Opera Widgets or Opera Unite applications.

Developers can build extensions with the same web standards they already use to build websites and web applications. Better yet, with only a few tweaks to their code, developers who have already authored a similar extension for other browsers will be able to share their creation with more than 50 million Opera users.