Yet again challenging Microsoft, Google has acquired Silicon Valley startup Upstartle and, in the process, its Writely web-based word processing software, which allows users to create documents online and share them with others, reports Bloomberg. The terms of the deal were not disclosed. The move signals that Google will be competing with Microsoft's Word and expanding into web-based office productivity software.

According to the Writely website, new registrations for the product have been "closed off…until we move Writely to Google's systems." The site asks visitors to leave their email address to be informed when registration reopens.

Writely contains RSS integration so users can track changes made to a document that they've shared with other and features revision history on every document, writes NetworkWorld. Users can post documents to a blog, as well as create web pages, from within Writely.

Writely uses AJAX programming controls, which allows for the creation of web-based applications that behave like desktop software. Google has used AJAX for Gmail and Google Maps.