HTML Zero → Mastery — Dictionary (Lessons 1

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A
addEventListener: JavaScript method to attach event handlers without inline attributes (e.g., elem.addEventListener('click', fn)).
Attribute: Extra information on an element’s start tag (e.g., lang, charset, rel, id).
<article>: Self-contained composition (e.g., a card or post) within the main content.
B
<body>: Document’s visible content container.
Blocking resource: Resource (often CSS/JS) that delays initial rendering until it’s loaded/processed.
<br>: Line break. Use sparingly—prefer paragraphs and CSS spacing.
Browser: The application that fetches, parses, and renders web pages.
Broken HTML: Invalid or malformed markup that can cause unpredictable rendering.
<button>: Interactive control; pair with JS listeners for behavior.
C
charset (meta): Declares character encoding, e.g., <meta charset="UTF-8">.
class (attribute): Token(s) used as styling/JS hooks (e.g., class="warning").
Console: DevTools tab showing logs, warnings, and errors from scripts.
Comment (): Note for developers; not rendered by the browser.
CSS: Presentation layer: layout, spacing, color, typography, responsiveness.
CSSOM: Tree of parsed CSS rules; combined with the DOM to create the render tree.
D
defer (script attribute): Downloads a script during parsing and executes after the document is parsed.
<details>: Native disclosure widget used for hints/solutions.
DevTools: Built-in browser tools to inspect and debug pages.
DOM: Document Object Model — the tree built by parsing HTML.
<!DOCTYPE html>: Tells the browser to use standards mode (avoid quirks mode).
E
Element: A complete unit of markup: the tag(s) plus its content and attributes.
<em>: Emphasized text that affects meaning.
Event listener: Function responding to user/system events (click, input, etc.).
F
Fetch: Retrieving a resource (like an HTML file) over the network or filesystem.
H
<head>: Metadata container: title, meta tags, links, etc.
<header>: Introductory content/navigation for a page or section.
Headings (<h1>…<h6>): Define the document outline; <h1> is the top-level heading.
hidden (attribute): Boolean attribute to hide content (e.g., toggle with JS by flipping elem.hidden).
<hr>: Thematic break (horizontal rule) between sections.
HTML: HyperText Markup Language — the structure and meaning of web pages.
<html>: Root element that wraps the entire page. Often includes a lang attribute.
I
id (attribute): Unique identifier for an element (id="themeBtn"), used to select it in JS or link targets.
Inline styles: CSS placed directly on elements via style="..."; discouraged in favor of classes.
Invalid nesting: Placing elements in disallowed positions, forcing the parser to auto-correct.
J
JavaScript (JS): Behavior layer: events, state, DOM/CSSOM updates, storage, fetch.
L
lang (attribute): Declares the language of the document/element (e.g., <html lang="en">).
<link>: References a stylesheet: <link rel="stylesheet" href="styles.css">.
localStorage: Key–value storage for persisting simple preferences (e.g., theme).
M
<main>: Primary content landmark of the page.
<meta>: Metadata element for character set, viewport, descriptions, etc.
N
<nav>: Section containing navigation links.
P
<p>: Paragraph of text.
Paint: Stage where the browser fills pixels (text, colors, borders) onto layers.
Parse / Parser: The process/tool that reads HTML/CSS and builds the corresponding trees.
Performance: How fast a page renders/responds; impacted by blocking resources.
Q
Quirks Mode: Legacy rendering mode triggered without a proper DOCTYPE. Avoid it.
R
rel (attribute): Relationship of a linked resource (e.g., rel="stylesheet" on <link>).
Render Tree: Structure created by combining the DOM and CSSOM for layout/paint.
Resources: External files referenced by HTML, including CSS, JavaScript, and images.
S
<script>: Loads and executes JavaScript. Use defer for non-blocking behavior.
Separation of Concerns: Keeping structure (HTML), presentation (CSS), and behavior (JS) in distinct layers.
src (attribute): Specifies the external resource for scripts (and other elements).
<strong>: Strong importance; conveys semantic emphasis.
<summary>: Label for a <details> disclosure widget.
T
<tag> (Tag): The markup keyword in angle brackets (e.g., <p> or </p>).
<title>: Page title shown in the browser tab and bookmarks.
U
UTF-8: Unicode character encoding recommended for modern pages.
URL: The address the browser loads when fetching a page or resource.
V
Viewport (meta): Controls layout viewport on mobile (e.g., width=device-width, initial-scale=1).