This document discusses responsive image techniques for adaptive web design. It begins by explaining browser sniffing versus feature testing, and recommends using feature testing to determine browser width, screen resolution, and bandwidth instead of browser sniffing. It then covers techniques like using background-size to control image sizes, SVG for smaller file sizes, and font-based solutions. The document also discusses server-side techniques like .htaccess rewrite rules and client-side techniques like picture and HiSRC. It advocates for a mobile-first approach using CSS media queries and a single pixel GIF for responsive images.