A HTML/CSS Prototyping Developer designs and constructs web page layouts or user interfaces using HTML and CSS. They create prototypes to visualize and test the functionality of web applications before they are fully developed. Their work involves coding, testing, debugging, and analyzing the performance of prototypes. They ensure that the design is responsive, user-friendly, and accessible across various devices. They work closely with designers and developers to implement changes, solve problems, and improve the overall user experience. They also take part in user research to understand user needs and incorporate feedback into the prototype.