LiveJS is/will be a Javascript based environment for livecoding or doing experiments on websites. It's a bookmarklet, which is "a small JavaScript program that can be stored as a URL within a bookmark in most popular web browsers or within hyperlinks on a web page."

It can be used on every browser and on every website.

It's capable to use live/flickr/twitter … streams and the resources of the webpage that it runs on. It also can receive OSC messages.