A Microsoft spinoff plans to release an open beta of a new mobile browsing user interface in mid-December.

ZenZui, the Seattle spinoff, was also set to announce on Tuesday it is changing its name to Zumobi.

Zumobi is offering a piece of software, currently only compatible with Windows Mobile phones, that works in connection with a back-end server and is designed to make mobile Internet use easier. The user interface is made up of 16 tiles on which users can easily zoom in and out. Each tile represents a Web page.

Zumobi's back-end servers are constantly updating the Web sites on the phone, so a user doesn't have to wait for the site to load after they click the tile. Users determine what site appears in each tile, and they can send tiles to each other.

The service will be free for end-users -- except for related mobile data network usage -- and advertising supported. Advertisers could sponsor specific tiles that might offer information users might want, such as traffic updates. If an operator preloads the software onto phones, the operator gets a cut of the advertising revenue.

Zumobi hopes to make the client available to many other types of phones, with the Research in Motion BlackBerry next in line and expected in the second quarter of 2008, said John SanGiovanni, co-founder and vice president of product and services for Zumobi. He recognizes that the advertising proposition is much more compelling if Zumobi is available on a wide array of handsets, but the company decided to focus on one phone at first to make the service very solid, he said.

The iPhone is also quite high on Zumobi's list, but the company doesn't want to officially say it will build a client for the phone until it sees the iPhone developer kit, which comes out next year. "This is about how you snack on content," he said. "So in that sense, we think iPhone users will love Zumobi."

Zumobi is designed to be able to work on a wide variety of hardware, including phones that have touchscreens, numeric keypads, and full keyboards and that operate in landscape or portrait modes.

Starting Dec. 14, Windows Mobile users can visit Zumobi's Web site to register for the beta. Users will be able to download the software directly to their phones.

The introduction of the public beta follows a closed trial that the company conducted starting in April with select content partners and operators.

SanGiovanni worked on the technology behind Zumobi while at Microsoft Research. He helped separate Zumobi out of Microsoft and into an independent company earlier this year.