MDN Web Docs is an excellent example of a Free and Open-Source (FOSS) platform. You can access HTML, CSS, and JavaScript documentation and examples on a well-organized website. Among the tools the ...

jsFiddle lets developers play with the three core elements of Web development. Check out this powerful application for rapid prototyping and testing.

HTML provides the structure, content and layout, CSS adds style and design, and JavaScript adds functionality and interactivity.