user interaction

Indeed, tradtional web apps make use of XHTML and CSS, but this is only an attempt to inscrease flexibility on styling and structuring issues or no more than readability. However, concerns of user interactions are not beeing touched by these technologies. Common technologies do not deal with interactions like drag'n'drop, autosuggestion or even to quash annoying page reloads on filling forms – to name but a few. Which technologies are able to face this issues adequately, without reinventing the wheel nor requiring exotic and/or proprietary plugins.