Silverlight is Microsoft’s cross-platform, Flash alternative, which is now available in beta for both Safari and Firefox. Eddie Hargreaves point out in Apple blog post that Silverlight will return official Microsoft support for Windows Media streaming to the Mac, including HD video support up to 720p.

Microsoft stopped development of the Windows Media Player for Mac and the last version is Windows Media Player 9, Since then primary Windows Media solution on the Mac has been from Flip4Mac, a plugin for running wmv media inside the Quick Time Player. Microsoft itself is distributing the Flip4Mac plugin. Microsoft is not going to support PPC mac for Silverlight as reported by TUAW.

Silverlight is available as a free download here.