This document provides an introduction to building modern websites using HTML5 and CSS3. It discusses several new features in HTML5, including semantic elements, the <canvas> element for 2D drawing, <audio> and <video> elements for multimedia, local storage APIs, and offline application support. The document also outlines some prerequisites for using these new technologies, such as installing the latest browsers. Finally, it notes that a sample website later in the tutorial demonstrates several HTML5 and CSS3 features.