В недавно вышедшем Firefox 3.1 Alpha 2 появилась начальная поддержка web worker threads:
http://developer.mozilla.org/web-tech/2008/09/04/web-workers-part-1/
"Some computations in JS take a long time, like this (incredibly poor!) implementation of the Fibonacci sequence
<...>
Thankfully preliminary support for web workers has landed in Firefox 3.1 Alpha 2 so that expensive computations like this can be moved off to a background thread. The user interface will remain responsive while the JS engine churns and navigating away from the web page will even pause its execution."
Будет Ъ?
