HTML (HyperText Markup Language) is the most basic building block of the Web. It defines the meaning and structure of web content. Other technologies besides HTML are generally used to describe a web page's appearance/presentation (CSS) or functionality/behavior (JavaScript). HTML developers are responsible for the complete end-to-end coding of websites. They provide technical support to users, direct projects, code websites, develop web-based applications, and perform testing on websites. They work with other coders, designers and content developers, which means that communication skills are important. HTML developers must be able to translate designs into code and write technical documentation. CSS developers are web professionals whose primary responsibility is to deliver a polished and styled product to a user's browser. Almost every website uses CSS. Most frontend or even full-stack developers could write the CSS code. But not all of them can fix every CSS bug or implement designs without convoluting HTML code or relying on JavaScript unnecessarily. A HTML/ CSS Developer's responsibilities would typically include: Translation of designer mock-ups and wireframes into front-end code Front-end integration with a back-end framework Optimize application for maximum speed and scalability Assure that all user input is validated before submitting to back-end Build reusable code and libraries for future use Integrate data from various back-end services and databases Cooperate with web designers to match visual design intent