Mobile Web Programming has a detailed writeup of the new HTML5 and W3C future standards support included in yesterday's iOS 4.2 release. These new APIs haven't been fully documented yet by Apple but these changes have been uncovered as part of Mobile Web Programming's own independent research. They include new standards like Accelerometer and Gyroscope support in the DeviceOrientation API, the WebSockets API that's part of HTML5, and information on how to invoke printing dialog in mobile Safari.
Some of the new functionality includes expansion of the
