"Piotr Zalewa has created a really great playground, jsFiddle, for testing sample code and playing with the Web. With an area for the holy trinity of the Web (HTML, CSS, JS) and an output region, you can get right to hacking. It goes beyond this though. You can also add resources, an Ajax echo backend, and auto load from a slew of JavaScript frameworks. You can also check out the examples and see great stuff such as Processing in action. And the finishing touch, share and embed." - xero from Bookmarklet