The first big blow to Flash was Apple's iOS. Now Adobe Systems' browser plug-in faces another major threat to its relevance: Microsoft has banned it and all other plug-ins from the "Metro" version of Internet Explorer 10.

Metro is the modern "touch-first" interface that plays a starring role in the radically new look of Windows 8, which Microsoft plans to release in 2012. Microsoft will ship the new OS with two versions of IE10, one for Metro and one a brushed-up version of the current Windows 7 interface. While the legacy version of IE10 will accommodate plug-ins, the Metro won't, IE team leader Dean Hachamovitch said in a blog post last night during the company's Build conference.

His words should be music to the ears of those who are critical of Flash and those who are fans of a new swath of Web standards often designed to replace Flash. Dean wrote:

Running Metro-style IE plug-in free improves battery life as well as security, reliability, and privacy for consumers. Plug-ins were important early on in the Web's history. But the Web has come a long way since then with HTML5. Providing compatibility with legacy plug-in technologies would detract from, rather than improve, the consumer experience of browsing in the Metro-style UI.

Adobe isn't putting all its eggs in the Flash Player basket when it comes to wooing developers. It's got a growing range of software including Edge, Muse, Wallaby, and the years-old DreamWeaver for those using Web standards. And Adobe has begun participating in Web standards development.

But Flash Player remains an important priority for the company as it seeks to attract developers who want to write software that can span many browsers and operating systems. Adobe is working hard to bring it to the mobile realm, notably with Android, and Adobe's Flash team was triumphant when a Flash-based game rose to the top of the iPad charts.

In addition, Adobe is pushing Flash ahead as fast as it can. The new Flash Player 11 has released release-candidate stage, bringing features such as accelerated 3D graphics and a 64-bit design. At the same time, Adobe is being more circumspect about the tasks best suited to Flash as HTML5, CSS3, faster JavaScript, and other Web standards advance. Those areas for Flash include games, advanced video, and companies' in-house applications.

Adobe didn't immediately respond to a request for comment.

Adobe isn't the only casualty of Microsoft's decision, though. Microsoft itself also loses out with its Silverlight plug-in, which never really succeeded in denting Flash's widespread use on desktop browsers.

Silverlight apps, though, can be converted to Metro apps, as Microsoft took pains to explain at the Build conference.