ECMAScript 5 was standardized in late 2009 but only recently has it has started showing up in browsers. It supersedes the 3rd edition, which was ratified in 1999. ECMAScript 5 is actually two languages, ES5/Default and ES5/Strict. Future versions are going to be built on top of ES5/Strict and it is recommended that the default version be avoided.
The ECMA working group in charge of the Common Language Infrastructure standard has produced released a working draft of the 5th edition. The CLI represents the subset of Microsoft’s .NET platform that has been placed in the care of Ecma International. Originally known as the European Computer Manufacturers Association, Ecma International both competes with and complements ISO.