As iOS, Android, and Windows 8 take the Web to smaller screens, designers are adopting techniques to make their websites usable on handheld devices. Responsive Web designs present different formatting and layout to suit the device on which their pages are displayed. Browsers choose the appropriate styles on page load, freeing website owners from having to maintain different sets of pages for different display scenarios.
The most common responsive method is to use CSS media queries to serve different style sheets (or parts of style sheets) based on the number of pixels available. Most often, this is applied to handheld devices such as smartphones, but it could be applied to 13-inch laptops, 30-inch TVs or Kindle-sized readers. Responsive designs respond to their environment.