slashdot has a link to AJAX or Asynchronous Javascript + XML. old: HTML + some (or a lot) of javascript inside them. new: javascript feeding XHTML to the browser. No more page loads. The only load is a huge javascript load. After that the UI experience is more subtle, with the javascript "engine" feeding the browser XHTML on demand. When the website needs data from the server, an HTTP request is made in the background by the javascript engine.

The description of how java script based websites are different than HTML based websites is explained well in this graphic

So now websites are applications, written in javascript. The "engine" will evolve into an OS, with multitasking, multithreading. The tabs in Firefox may work more like application switching than ever before. It'll have security issues up the wazoo.

Java has had applets for a long time. Its zero integration with the browser made it not so useful. Its got a full, featureful library and a configurable security model.

Okay so who wants to be the first to write a bittorrent client in javascript? Give it the features of Azureus. The web solves the application delivery and versioning problem. Need a new version? chances are you just loaded the latest version. Application size becomes a problem. At least images are loaded on demand. If you did that I'm sure someone would offer you a well paid job to do javascript all day long. oh the humanity. grin.