A CSS Sprites developer combines multiple images into a single file to reduce server requests, improving website performance. They use CSS to control the display of individual images from the combined file, positioning them precisely for correct display. This involves calculating the exact position of each image within the sprite sheet. They also ensure that the sprite sheet is optimized for minimum file size without compromising image quality. Their work requires a deep understanding of web standards, graphic formats, and CSS. They frequently collaborate with UI/UX designers and backend developers to ensure seamless visual experience and optimal website performance.