Silverlight is a cross-browser, cross-platform plug-in for delivering the next generation of media experiences and rich interactive applications (RIAs) for the Web.

Silverlight - The next generation web experiences
Today at the National Association of Broadcasters (NAB) conference, Microsoft is again demonstrating how we are enabling our customers to have richer experiences on the web by announcing Microsoft Silverlight - a new, cross-platform, cross-browser... More...

Deliver media experiences and rich interactive applications (RIA) for the Web that incorporate video, animation, interactivity, and stunning user interfaces.

Seamless, fast installation for users, thanks to a small, on-demand, easy-to-install plug-in that is less than 2 megabyte (MB) and works with all leading browsers.
Consistent experiences between Macintosh computers and Windows-based personal computers without any additional installation requirements.
Create richer, more compelling Web experiences that take greater advantage of the client for increased performance.
Stunning vector-based graphics, media, text, animation, and overlays enable seamless integration of graphics and effects into any existing Web application.
Enhance existing standards/AJAX-based applications with richer graphics and media, and improve their performance and capabilities by using Silverlight.