In HTML5, the `summary` element is used in conjunction with the `details` tag to create a clickable summary title that can expand or collapse hidden content when clicked. It must be the first child of `details`. By default, the content inside `details` is hidden, and clicking the `summary` toggles its visibility. The `open` attribute can be used to set the default expanded state. Nested usage and JavaScript interaction are supported, with the `toggle` event responding to state changes. It is suitable for scenarios like FAQs, code examples, and form options. Custom styling is possible, but accessibility considerations are necessary. Most modern browsers support it, and polyfills can ensure compatibility with older browsers. Performance optimization is required when used extensively. It can be combined with various HTML elements and supports dynamic content loading. By default, content is hidden when printing, but CSS can force it to display.
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The `<mark>` tag in HTML5 is used to highlight text content with semantic meaning, not limited to stylistic effects. Browsers display it with a default yellow background, but the style can be customized via CSS. It is commonly used in scenarios such as highlighting keywords in search results, emphasizing key points in educational content, and more. Compared to using a `<span>` with CSS, `<mark>` offers stronger semantic advantages, supports nesting and dynamic manipulation, and is compatible with modern mainstream browsers. JavaScript can be used to implement dynamic highlighting functionality. Special considerations are given to accessibility and print styling. Proper use of `<mark>` can enhance content readability and user experience, though it does not directly impact SEO rankings. Creative applications include progressive highlighting, multi-color classification systems, and note annotations.
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The HTML5 `<figcaption>` tag is specifically designed to provide a title or caption for a `<figure>` element and must be used in conjunction with `<figure>` to form a complete structure of media content with a description. It must be a direct child of `<figure>`, and a `<figure>` can contain only one `<figcaption>`, which can be placed as either the first or last child element. The article details how `<figcaption>` works with different media types, such as images, code blocks, and videos, and provides styling customization techniques, including basic styling, image caption styling, and code block caption styling. It also covers its application in responsive design, optimizing captions for different screen sizes through media queries. The importance of accessibility is emphasized, ensuring a logical DOM order with associated content and avoiding reliance solely on visual styling to convey information. Additionally, the article demonstrates combining `<figcaption>` with tables and implementing interactive captions using JavaScript. Finally, it offers styling optimization suggestions for print media.
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The HTML5 `<figure>` tag is a semantic container used to wrap independent media content and its caption. Typical applications include displaying images, code, videos, and charts. Its basic structure consists of a media element and an optional `<figcaption>` title, supporting multiple content combinations and responsive design. Custom styling and layout can be applied via CSS, while JavaScript enables interactive functionality. Accessibility is emphasized, requiring attention to alt text and keyboard navigation. Compared to generic containers like `<div>`, it offers greater semantic advantages, benefiting SEO optimization and screen reader recognition. All modern browsers provide excellent support, though specific CSS declarations may be needed for older versions of IE. Practical use cases include blog illustrations and product showcases. Its semantic nature makes it an ideal choice for structuring media content.
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The HTML5 `<aside>` tag is a semantic element used to define non-primary content on a page, typically appearing as a sidebar or supplementary material. It is suitable for displaying advertisements, quotes, annotations, and other auxiliary information. The basic usage involves wrapping text, images, or other elements within a pair of opening and closing tags, with styles customized via CSS. Its core value lies in semantic clarity, explicitly marking sections that are related to but independent of the main content. Common use cases include sidebars, navigation menus, article addenda, and ad placements. Layout implementation relies on CSS, with flexible solutions like Flexbox enabling responsive designs. Note the semantic distinction from `<div>`—prefer `<aside>` to enhance accessibility, ideally paired with ARIA attributes. Browser compatibility is excellent, with full support in modern browsers. It can be used alongside other semantic tags like `<main>` and `<article>`. For printing, non-essential content can be hidden.
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The HTML5 `<section>` tag is a semantic element used to define independent sections or blocks within a document that contain related content, such as article chapters or functional modules. Unlike `<div>`, `<section>` has clear semantic meaning, improving readability and SEO. The basic usage involves wrapping content inside the `<section>` tag, typically paired with a heading. `<section>` is suitable for dividing logically independent content blocks. Unlike `<article>`, which is used for complete, standalone content, `<section>` is intended for document chapters. It can be nested to express complex structures and is ideal for article chapters, functional blocks, or tabbed content. When using `<section>`, avoid overuse, pair it with a heading, and do not replace `<article>`. Custom styling can be applied via CSS. Its semantic features enhance accessibility and can be further optimized with ARIA attributes.
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The HTML5 `<article>` tag is used to define independent, self-contained content blocks such as news articles or blog posts, whose content remains meaningful even out of context. Unlike the generic container `<div>`, it carries explicit semantic value, enhancing document structure and accessibility. An `<article>` can contain multiple `<section>` elements and supports nested usage, such as in comment-reply scenarios. Each `<article>` should include a heading element to improve accessibility. Practical applications include news aggregation pages and e-commerce product listings. Combining it with Schema.org markup can optimize SEO. For dynamic content loading, `<article>` elements can be inserted via JavaScript. Browsers render it as a block-level element by default. In responsive design, it can work with CSS Grid and serve as a container for Web Components' Shadow DOM. Using the `<article>` tag effectively improves webpage semantics and machine readability.
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The `<main>` tag in HTML5 is used to define the main content of a document, helping to identify the core of the page and improve accessibility. Each document should have only one `<main>` tag, which should not be nested within tags like `<article>`. Unlike `<body>`, it focuses solely on the core content and is often used in conjunction with tags like `<article>`. It has practical applications in blogs, e-commerce, and other scenarios. Accessibility considerations, such as adding skip links, are important. Browser compatibility is good, though older versions of IE may require a polyfill. The content can be dynamically updated via JavaScript. By default, it is a block-level element and can be styled. It also has specific usage patterns in frameworks like React and Vue.
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The HTML5 `<nav>` tag is a semantic element specifically designed for defining navigation links, enhancing both web accessibility and SEO performance. Typically, `<nav>` contains primary navigation menus, breadcrumb trails, or footer navigation. The basic usage involves placing unordered lists or direct links within the `<nav>`. Compared to traditional `<div>` implementations, `<nav>` offers stronger semantic value. When using it, focus on primary navigation scenarios and avoid overuse to maintain clarity. Accessibility can be improved with ARIA labels and keyboard navigation support. For responsive design, it can be combined with hamburger menus for mobile adaptation. Advanced techniques include dropdown menus and sticky navigation bars, but be cautious of common pitfalls like excessive nesting or neglecting accessibility. All modern browsers support the `<nav>` tag, and performance optimization can be achieved by reducing DOM nodes and using CSS sprites. For SEO, it’s recommended to use structured data and descriptive link text. Practical examples demonstrate navigation implementations for e-commerce sites and single-page applications.
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The `<footer>` tag in HTML5 is used to define the footer of a document or section, containing content such as copyright information, author details, and contact information. It enhances code readability and helps search engines understand the page structure. The `<footer>` can appear within tags like `<body>` or `<article>`, and its scope depends on its placement: directly inside `<body>` it represents the footer of the entire document, while nested within other tags it acts as the footer for that specific section. Common content includes copyright notices, contact details, and related links. CSS can be used to customize its styling. For SEO, avoid keyword stuffing, maintain link relevance, and consider adding structured data to enhance semantics. In Single-Page Applications (SPAs), special handling is required to ensure correct positioning. Browser compatibility is excellent, with support across all modern browsers. Creative uses include serving as the bottom of modal dialogs or card components, as well as optimizing display for printed pages.
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