A HTML/CSS/Bootstrap developer designs and implements web page interfaces. They use HTML (HyperText Markup Language) to structure content on the web and CSS (Cascading Style Sheets) to style this content. Bootstrap, a popular CSS framework, is used to create responsive and mobile-first websites. Developers use these tools to create layouts, buttons, forms, navigation, and other elements of a website. They also ensure compatibility across different browsers and devices. They work closely with backend developers and designers to create an optimal user experience. They may also conduct website performance tests and troubleshoot issues.