<ul>- Unordered list

The `<ul>` tag in HTML is used to create unordered lists, typically paired with `<li>` tags. By default, items are marked with bullet points, and nesting is supported to achieve multi-level lists. Traditional attributes like `type` can define marker styles, but modern development recommends using CSS for styling. With CSS, you can customize marker styles, achieve horizontal layouts, or add hover effects. Practical applications include navigation menus and feature lists. It differs from other list tags like `<ol>` and `<dl>`, and accessibility considerations should be noted, such as avoiding excessive nesting and adding ARIA roles. All major browsers support the `<ul>` tag, and JavaScript can dynamically manipulate list content.

<data>-machine-readable data

The HTML5 `data` tag is a semantic element used to associate human-readable content with machine-readable data. It stores machine-readable values through the `value` attribute while displaying human-readable text. Common use cases include displaying product information, unit conversion, and data identification storage. Unlike specialized tags like `time` and `meta`, the `data` tag is a universal data container. In practical applications, it can be combined with microdata to enhance SEO or paired with JavaScript for dynamic updates. Modern browsers widely support this tag, which is often used on e-commerce websites to display prices, inventory, and other information, as well as for academic and statistical data presentation. Best practices recommend providing complete human-readable content, using standardized data formats, and combining it with CSS for conditional styling. The `data` tag effectively bridges the gap between human and machine data understanding, improving the structural organization of web information.

The `<dialog>` element—a dialog window.

The HTML5 `dialog` tag is used to create modal or non-modal dialog boxes, providing a semantic way to implement pop-ups without relying on JavaScript libraries. Basic usage includes two display modes: `showModal` (which blocks interaction with the rest of the page) and `show` (which allows it). CSS can fully customize the dialog's appearance, including the backdrop styling. The dialog works well with forms, making it ideal for confirmation scenarios. It supports animations and event handling, such as `close` and `cancel` events. Nested dialogs and return value functionality are also possible. Browser compatibility should be considered. Best practices include focus management and accessibility. In frameworks like React, dialogs can also be used, with advanced features like drag-and-drop. For performance optimization, avoid loading excessive content. Error handling should account for `InvalidStateError`. Finally, dialogs can be encapsulated as reusable web components.

`<details>` - Expandable details

The `<details>` tag in HTML5 is used to create collapsible content sections and must be paired with the `<summary>` tag. By default, the content is hidden but can be set to expand initially using the `open` attribute. It supports nested usage and multi-level collapsing. Styles can be customized via CSS, and JavaScript can be used for interactivity by listening to the `toggle` event. While modern browsers generally support it, IE and older versions of Edge are incompatible, though polyfills can resolve this. It is commonly used for FAQs, code displays, optional form fields, and similar scenarios. Accessibility and performance optimization should be considered, avoiding embedding excessive resources within collapsible content. It can be combined with other HTML elements but requires attention to structural integrity. CSS and JavaScript can enable animation effects. It can also be used in frameworks like React and Vue, and custom web components can be created to enhance functionality.

<summary>-Detailed summary

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.

<mark>-Highlight the text Translate this sentence into English, output only plain text, do not output any other content

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.

<figcaption>- Media content title

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.

<figure>- Media content combination

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.

<aside>- Sidebar content

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.

<section> - document section

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.