CSS1, introduced in 1996 by the W3C, revolutionized web development by separating HTML content from presentation. It introduced selectors, improved typography, and layout features like the box model, despite initial challenges with browser compatibility. As the bedrock for CSS2 and CSS3, CSS1's principles still impact modern design, SEO, and cross-browser compatibility. Its legacy endures in contemporary practices, and its foundation is built upon by advanced layout systems like CSS Grid and Flexbox, influencing developers to adapt and learn in the ever-evolving digital landscape.