A developer is responsible for designing and implementing user-friendly websites using CSS (Cascading Style Sheets) Level , a style sheet language used for describing the look and formatting of a document written in HTML. They focus on layout, visual appearance and usability, ensuring websites are both functional and aesthetically pleasing. They work closely with UX/UI designers and web developers to integrate designs seamlessly into existing systems. Moreover, they troubleshoot and resolve CSS issues, optimize web pages for maximum speed and scalability, and ensure that all web design is responsive for mobile devices. They also maintain and update websites as needed.