A front-end web developer is responsible for implementing visual elements that users see and interact with in a web application. They are usually supported by back-end web developers, who are responsible for server-side application logic and integration of the work front-end developers do.
Why do I see duplicate challenges? You'll see duplicates because a question may fall into different categories. We keep them here bec ause we believe that it is good to sporadically review old challenges. They are optional if already completed-- but reviewing them (and more importantly redoing them with the new knowledge) will ensure that you've let the material sink in.