This post over on Mozilla's "hack" site reports that Firefox 3.6 will be able to detect whether a laptop or mobile device is horizontal or vertical by using--if installed--their built-in accelerometers. Currently Safari does this on the iPhone and iPod Touch, enabling Web surfers to view the Internet vertically or horizontally.
Mozilla's Christopher Blizzard also uploaded a video demonstration on how this will work, rotating a laptop on its side while the objects within the browser remain stationary horizontally and vertically in relation to the viewer. Frankly, we're not sure why anyone would want to browse with the laptop sitting on its side, but the effect is cool nonetheless.
"Originally built as something that we would include for our upcoming mobile browser release, we’ve made it available on desktop systems as well," he said. "Many modern Macbooks and Thinkpads contain devices and drivers that expose this information. We’ve added support for Linux, Macs and some Thinkpads where drivers and devices are available."
Mozilla's Paul Rouget also added that the latest "trunk" of Firefox already has the orientation feature. Web pages must insert a special "event listener" in order for the browser to utilize the device's accelerometer.