Microsoft's bringing Silverlight to cell phones, partnering with Nokia to bring the rich Internet app browser plug-in to devices that use Nokia's popular S60 software platform.

Nokia will also make Silverlight available on its Series 40 devices and its Internet Tablet devices, the companies are expected to announce Tuesday.

The strategy to get Silverlight on mobile devices -- and particularly on the Symbian OS -- is part of Microsoft's effort to make the browser plug-in a cross-platform, cross-browser product in order to get as much penetration as possible on the Web. The company is also working on a version of Silverlight for Windows Mobile, a beta version of which is due out soon.

Microsoft is coming from behind. Adobe has had a strong mobile presence for Flash for years. It has distribution agreements with 18 of the top 20 device manufacturers worldwide including Nokia, and according to Adobe, 450 million devices have been shipped so far with Flash Lite, which is a trimmed down version of Flash. That, of course, compares to zero for Microsoft. According to Adobe, Flash Lite has seen a 150% growth in the past year.

While Microsoft's early Silverlight mobile strategy will focus on Symbian and Windows Mobile, Adobe also supports BREW and a few other proprietary operating systems.

Though most of Adobe's strategy has thus far revolved around Flash Lite, some devices also ship with the full version of Flash, including a few from LG like the LG Chocolate and Voyager. Adobe also offers a service called Flash Cast that includes channels of content, a home screen called Flash Home, and tools that show software developers how their Flash apps would look on specific mobile devices.

Still, Nokia gives Microsoft a good footprint. Nokia's S60 platform is the most popular smart phone software platform worldwide, with more than 53% market share in the fourth quarter of 2007, according to analyst firm Canalys.

"We can't pretend to be a really ubiquitous play without being a partner with Nokia and Symbian," John Case, GM of Microsoft's developer division, said in an interview.

Nokia licenses its S60 platform, which uses the Symbian mobile operating system, to other major mobile device manufacturers, including LG Electronics and Samsung, though only Nokia uses S60 in the United States, according to Nokia's own Web site.

Much of Microsoft's strategy for Silverlight thus far has revolved around creating content partnerships rather than relationships with hardware manufacturers. Though Microsoft says there are around 8,000 Silverlight apps today and the company is announcing more on Wednesday at its MIX conference for Web developers, the deal with Nokia could be a sign that there's enough Microsoft dedication to Silverlight that Nokia is convinced the content will come, as it wouldn't make sense to include a multi-megabyte application on a hardware-limited mobile device if it isn't going to be used.