Microsoft Silverlight

Microsoft Silverlight is a browser plugin that allows web applications to be developed with features that characterize a rich internet application: animation, vector graphics and audio-video playback. Silverlight competes with products such as Adobe Flash, Adobe Flex, Adobe Shockwave, Java FX, and Apple QuickTime. Version 2.0 brought improved interactivity and allows developers to use .NET languages and development tools when authoring Silverlight applications.
Silverlight was developed under the codename Windows Presentation Foundation/Everywhere (WPF/E). It is compatible with multiple web browser products used on Microsoft Windows and Mac OS X operating systems. Mobile devices, starting with Windows Mobile 6 and Symbian (Series 60) phones, will also be supported.[1]. A third-party free software implementation named Moonlight is under development to bring compatible functionality to GNU/Linux.

Silverlight provides a retained mode graphics system, similar to WPF and integrates multimedia, graphics, animations and interactivity into a single runtime. It is being designed to work in concert with XAML and is basically the a set or .NET classes scripted with JavaScript. XAML can be used for marking up the vector graphics and animations. Textual content created with Silverlight would be more searchable and indexable than that created with Flash as it is not compiled, but represented as text (XAML).[2] Silverlight can also be used to create Windows Sidebar gadgets for Windows Vista.[3]
Silverlight supports playback of WMV, WMA and MP3 media content[4] across all supported browsers without requiring Windows Media Player, the Windows Media Player ActiveX control or Windows Media browser plugins. Because Windows Media Video 9 is an implementation of the SMPTE VC-1 standard, Silverlight also supports VC-1 video, though still only in an ASF file format. Furthermore, the Software license agreement says VC-1 is only licensed for the "personal and non-commercial use of a consumer".[5] Silverlight does not support playback of H.264 video.
Silverlight makes it possible to dynamically load XML content that can be manipulated through a DOM interface, a technique that is consistent with conventional Ajax techniques. Silverlight exposes a Downloader object which can be used to download content, like scripts, media assets or other data, as may be required by the application.[6] With version 2.0, the programming logic can be written in any .NET language, including some common dynamic programming languages like Ruby and Python.