A CSS//JavaScript/jQuery/XML developer designs, develops, tests and maintains websites and web applications. They use for structuring and presenting content, CSS for layout and design, and JavaScript/jQuery for functionality and interactivity. XML is used for storing and transporting data. They create responsive designs, ensure cross-browser compatibility, troubleshoot issues, and optimize performance. They also work closely with back-end developers to integrate server-side code. Their role requires understanding of user experience design and SEO principles, and often involves collaboration with designers and other stakeholders. They continuously learn new technologies to stay updated.