Use enough Web applications, and you'll grow very familiar with one common complaint: Anytime you're offline, you can't get to your data. But a growing number of applications are working to change that.

Zimbra, a popular open-source e-mail application, added an offline version called Zimbra Desktop back in March. Mozilla has announced that Firefox 3 will support caching to allow Web apps to work offline. And Adobe's desktop Ajax application framework called AIR will offer some support for offline data. But as it often does, Google has made the biggest splash so far with the Gears API it announced in May.

Google released Gears along with the first app to make use of it, a new version of Google Reader that allows for offline reading of RSS feeds. Other companies have begun to use the Gears framework, too; the first one I found to have implemented it is the online to-do list tracker Remember the Milk.

Getting into Gears
Both Google Reader and Remember the Milk have taken the same simple approach to offline support. Click the little green arrow icon on the toolbar at the top of either to download and cache the data you'll need to work offline. Once you're synced up, you can unplug your connection and keep working, even if you close and reopen your browser. When you're ready to reconnect, click the blue arrow icon in the same location, and your changes migrate back online.

The Gears-enabled Reader works quite well, though its offline support is a bit rudimentary. Full-text feeds such as Engadget and Techcrunch work best, of course, but even in those I'd like to be able to tell Reader to also sync images in the feeds, and to boost the number of posts it syncs for offline reading. Stranger still, if you're browsing online and you click the offline button, you're unceremoniously dumped back at the top of the feed you're reading, and any feed-based images that you're viewing go away.

Remember the Milk has some similar issues. Delete a task in offline mode, and there is no way to recover it, though you can easily undo that action online.

Most of all, though, going offline with a Gears app requires some planning. Don't expect to just boot up your PC without a connection and start working in Reader. With current Gears apps, you'll want to start with a live connection and switch them all into offline mode before you dump your connection. It would be nice to have the option to sync automatically whenever you're online.