This document discusses using HTML/CSS in WordPress themes. It recommends using the Underscores starter theme to reduce time and effort. The Underscores theme provides default pages and structures that save developer hours. Key theme files like functions.php, header.php and footer.php are outlined. Styling elements with style.css is also covered. Child themes are recommended over directly modifying themes to avoid issues with updates. The document concludes with a practical example of creating a custom template file to build homepage slices directly in WordPress.