Google has also updated the Android mobile Web browser, with support for a quartet of APIs (application programming interfaces) from the emerging standard. That's significant because now browser-based applications can act much more like native applications. For example, the HTML 5 Database API supports client-side databases using SQL, to store data such as Web e-mail messages locally. This is now a feature of the browser in Android 2.0. In addition, the HTML 5 Application Cache lets developers store application functions and the UI, in JavaScript and Cascading Style Sheets, so users can access them offline.

Other browser improvements include: the HTML 5 Geolocation API, opening up information on the device's location; support for full-screen video; a new URL bar that users can tap for instant searches and navigation; bookmarks outfitted with Web page thumbnails; and double-tap zoom.

While Verizon's Droid phone will run Android 2.0, it's uncertain which other recently introduced or currently available phones will be able to use the software. For example, Motorola's Cliq, expected to go on sale in early November, runs Android 1.5. It's unclear whether users will be able to upgrade the phone to Android 2.0.

Google said it's up to carriers and handset makers. "Because Android is open source, all software updates we release are available for carriers and handset makers to take and update their current or future Android-powered devices," Katie Watson, a Google spokeswoman, said via e-mail. Past updates to the operating system have been automatically pushed out to the few available models.

It's possible that hardware requirements could prevent some devices from upgrading to the newest software. In addition, Greengart wonders if users of devices such as the Cliq or the Sense, with custom user interfaces, would have to also update the user interface after receiving the new operating system.