The "Robust" principle is a cornerstone of web accessibility, ensuring that your content remains usable as technology evolves. This principle focuses on making sure your web pages work not only with today's browsers and devices, but also with assistive technologies like screen readers, and even with tools that might be developed in the future. The key to achieving robustness is to use semantic HTML—that is, using HTML elements according to their intended purpose, so that both machines and people can interpret your content correctly.

When you use semantic HTML, such as <article>, <header>, <nav>, and <footer>, you provide clear meaning and structure to your content. Assistive technologies rely on this structure to help users navigate and understand web pages. If you use non-semantic elements like <div> and <span> for everything, you risk making your content confusing or even invisible to users who depend on assistive tools. Robust design means thinking beyond just visual presentation; it means building websites that communicate effectively with all technologies, now and in the future.