Is a simple PHP-and-cookies based solution to adapt pieces of your web site's content depending on the user's device screen width.

• Allows for a more highly configurable responsive design
• Provides the flexibility for custom page elements without the drawbacks of a devoted "mobile" site
• Provides a fallback for devices with JavaScript disabled

RESS was originally suggested by lukew in RESS: Responsive Design + Server Side Components, and uses the screen width cookie from MattWilcox's Adaptive Images.

Simple RESS by Matt Stauffer is licensed under a Creative Commons Attribution 3.0 Unported License