High resolution devices (the future)

Devices and their capabilities are changing all the time. Indeed, it isn't just different viewport sizes we must contend with. Already, we need to consider viewports that have higher resolution displays. The iPhone 4 was the first widely used device to implement a high-resolution display. Its screen is 960 by 640 pixel resolution at 326 pixels per inch, double the resolution of the prior version (iPhone 3GS) and double the pixel per inch density of laptops such as the 2011 15" MacBook Pro. Expect many more devices from tablets and laptops to desktop screens to follow suit. Thankfully, our responsive tools already provide us with the capabilities to support enhancements for these devices.

Let's suppose we wanted to load a higher resolution version of a site logo for users of high-resolution displays. It's a situation I encountered when performing a recent redesign of my own website at http://www.benfrain.com. Here is the markup for my logo area:

<div...