Gmail and Ajax. Introduction of jQuery, Prototype and other JS frameworks. Birth of Firebug
Node is conceptually composed of three layers of functionality: The underlying core engine, a number of core modules that add provide utility functions and APIs, and community-created modules for everything else.
Node.js is really two things: a runtime environment and a library. To install: https://github.com/joyent/node/wiki/Installation Linux: apt-get, rpm or make. Windows: untar the package and run exe.