The release of ASP.NET 2.0 introduces an alternate way to specify renderings of controls through a technology called control adapters. If you have heard of control adapters at all, it is probably in the context of providing alternate renderings of controls for mobile devices. They actually serve a more general purpose of providing a way of completely changing the rendering of a control based on the browser type of the client, which turns out to be useful in a number of situations.
Mobile device rendering is still the most obvious application of control adapters. For example, for a mobile phone, the control contents should render as WML instead of HTML. Ideally, developers would still use familiar ASP.NET controls, like Calendar and GridView, but when they are accessed by a WML device, a control adapter would kick in and provide an alternate rendering that would work within the constraints of the client device. With an updated collection of control adapters released as new devices come onto the market, developers would only have to update their list of control adapters, and suddenly their Web content would be available to these new devices without changing any of their actual code or page content.