You are primarily involved in the technical development of websites, i.e., programming and implementation.
You are (usually) given a design completed by a web designer, which you then implement technically. In rare cases, you are responsible not only for the implementation, but also for the design itself.
You develop a concept for the technical implementation and discuss it with the project managers, consultants, and clients.
You implement the website using languages such as HTML, CSS, JavaScript, ASP, .NET, PHP, and others. You are also familiar with database systems and SQL.
You may also be responsible for the backend of the website and content management system, modifying it for clients and adding new functions.
You comment on and document your code for the website.