The New York Times recently launched a Web app that formats articles the way it does on its physical page, but ReadWrite points out that it doesn’t work on all devices.

The Times calls its new app “Today’s Paper” because it attempts to mimic the day’s printed paper as closely as possible, as long as the subscriber is using Chrome or Safari on an iPad or is using a desktop computer.

“Soon after we launched our experimental Web App we discovered that Today’s Paper was one of the most popular sections,” Denise Warren, executive vice president of digital products and services at The New York Times, said. “This new reading experience is the next step in our ongoing process to develop new and valuable digital products that offer our subscribers other innovative ways to access our content.”

If you’re using an Amazon Kindle Fire, you’re out of luck. The tablet only allows for the use of the Silk browser, which the Times does not support. Nor does Today’s Paper support the mobile versions of Firefox. It also doesn’t support any smartphones.

The app is part of a trend toward “responsive design,” meaning that a page will reformat itself for a device that a user has. A responsive website delivers versions designed especially for tablets, desktops and smartphones.

The support for a limited number of devices runs contrary to the philosophy of responsive design and might remind some users of the “Browser Wars” of the ‘90s, with the infamous “Best viewed in…” buttons for Internet Explorer and Netscape Navigator.

Even though Amazon’s Kindle Fire has nowhere near the market share that Apple’s (News – Alert) iPad does, it makes sense for designers to be compatible with less popular devices. Being as platform-agnostic as possible is a way of “future-proofing” a Web app. Although the iPad currently rules the tablet market, there’s no guarantee that it will continue to do so in the future.

For more on this topic as well as other major innovations in HTML5, join us at DevCon5 December 10-11 in Los Angeles/Universal City, California.