What are Control Adapters ?

Control adapters are simply a way of providing different renderings for controls without actually modifying the controls themselves. Because control adapters are designed to provide alternate renderings for different clients, you specify control adapter mappings in a .browser file, which is where associations between User Agent strings and browser capabilities are defined.

The control adapter class itself must inherit from the System.Web.UI.Adapters.ControlAdapter, which is an abstract base class that looks much like the Control base class, with events for Init, Load, PreRender, and Unload, as well as a virtual Render method.