Microsoft Corp. clarified this week that the upcoming Office Web—a lightweight version of its Office suite that runs as an online service—will be available to users running Mac OS X and Linux, as well as from Apple's iPhone.

In a post to the Microsoft-run Channel 10 blog, someone identified as Sarah Perez spelled out system requirements for Office Web. According to Perez, the online versions of Word, Excel, PowerPoint and OneNote will be accessible not only from Microsoft's own Internet Explorer (IE) and within Windows, but also from Mozilla's Firefox and Apple's Safari browsers running on Mac OS X and Linux.

Firefox comes in versions for Mac OS X, Linux and Windows, while Safari has editions for both Mac OS X and Windows. Together, Firefox and Safari accounted for more than 26 percent of all browsers used during October, Web metrics firm Net Applications reported earlier this month. Microsoft's own IE, meanwhile, owned 71 percent of the browser usage share in October.

Last month, when Microsoft confirmed Office Web, it said that both Firefox and Safari would be supported but did not specifically say that the online applications would be available to non-Windows users.

And users of Apple's iPhone will be able to access Office Web, Perez said. The iPhone includes a scaled-down version of Safari.

The online suite, which is slated to debut at the same time Microsoft rolls out what it's now calling Office 14, the next upgrade of its business suite cash cow, will also be the first from Microsoft to run on the open-source Linux operating system.

Microsoft has not set a launch date for Office Web—Office 14 is expected to debut in late 2009—nor has it said whether it will be available to users free of charge, as is Google's Docs, and if not, how it priced the service.

A private technology preview of Office Web will begin later this year.