Rich Internet Application
Microsoft Silverlight
Silverlight enables development of the next generation of Microsoft .NET-based media experiences and rich interactive applications (RIAs) for the Web. Silverlight is delivered as a cross-platform and cross-browser plug-in that exposes a programming framework and features that are a subset of the .NET Framework and Windows Presentation Foundation (WPF).

It is combination of different technolgoies into a single development platform that allows you to select tools and the programming language you want to use. Silverlight integrates seamlessly with your existing Javascript and ASP.NET AJAX code to complement functionality which you have already created.

Silverlight aims to compete with Adobe Flash and the presentation components of Ajax. It also competes with Sun Microsystems' JavaFX, which was launched a few days after Silverlight.
Features :

»  A built-in CLR engine that delivers a super high performance execution environment for the browser.     Silverlight uses the same core CLR engine that we ship with the full .NET Framework.

»   Silverlight includes a rich framework library of built-in classes that you can use to develop
     browser-based applications.

»  Silverlight includes support for a WPF UI programming model. The Silverlight 1.1 Alpha enables you     to program your UI with managed code/event handlers, and supports the ability to define and use
    encapsulated UI controls.

»  Silverlight provides a managed HTML DOM API that enables you to program the HTML of a browser     using any .NET language.

»  Silverlight doesn't require ASP.NET to be used on the backend web-server (meaning you could use     Silverlight with with PHP on Linux if you wanted to).
Advantages :

»  Support for the .NET Framework and Base Class libraries.

»  Styles and Skinning Support.

»  Rich Controls.

»  Advanced Support for Networking.

»  Numerous of built-in controls.

»  Improved Server Scalability.