HTML, CSS, and JavaScript each play an important role in building a website. HTML provides the structure of a web page by organising the content such as headings, paragraphs, and images. On a KardiaSafe website, HTML would be used to display information about the smart medical bracelet, its features, and how it helps elderly users stay safe through health monitoring and emergency alerts. CSS is responsible for styling the page by controlling colours, fonts, and layout. JavaScript adds interactivity, such as buttons, forms, or animations that improve the user experience.