How a web page is structured, styled and made interactive: HTML elements and attributes, CSS selectors and the cascade, and JavaScript variables, functions and DOM manipulation.
Core rules
HTML skeleton: , , (title, meta, style or link) and . Tags nest, and most need a closing tag.
Common elements: h1–h6, p, a href, img src alt, ul/ol/li, table/tr/th/td, form/input/label, div and span.