This document provides an introduction to HTML, CSS, and JavaScript. It begins with explaining how client-side and server-side code works. It then defines HTML as the standard markup language for web pages and lists some commonly used HTML tags. CSS is introduced as the style sheet language used to describe the presentation of HTML documents. JavaScript is explained as the programming language used to create interactive effects in web browsers. The document concludes by covering JavaScript syntax like variables, functions, and some common methods.