Microsoft has published a plugin called Silverlight (the word plugin reminds us of Flash, one of the most accepted plugin-based technologies) which allows us to encode with sturdy, compiled languages (such as C# and VB.NET). This plugin incorporates a lite version, that is the .NET Framework, which offers us the possibility to take advantage of everything offered at the client side while implementing a new markup language called XAML. The advantages of using Silverlight are as follows:
Our applications are sturdier; for example, allowing us to implement automatic unit testing at the client side.
We can decouple business presentation and implement an architecture at the client side.
We can decouple roles. While a designer can deal with presentation, we as developers are able to focus on the business of building the application.
Our application is more scalable (we free up resources on the server) and we do not depend on tricks to maintain application status.
We can have a standard XAML implemented the same way in every single browser. No more headaches such as, "it looks good in IE6 but not in IE7, or Firefox, and so on".
In addition, Silverlight is multi-platform (for example, Windows or Mac) and multi-device (computers, mobile devices with Symbian or WP7 support, for instance, among others).