HTML is the markup language used to structure web page content and describe headings, paragraphs and lists. The most established version is HTML 4.01, while HTML5 is gaining popularity. CSS describes how HTML content should look by controlling fonts, colors, layout and other presentation elements. JavaScript adds interactivity to web pages by manipulating HTML elements, styles and the browser. It is used for form validation, animations, remembering user information between visits and building interface widgets.