Block-level elements - HTML: HyperText Markup Language 编辑
HTML (Hypertext Markup Language) elements historically were categorized as either "block-level" elements or "inline-level" elements. Since this is a presentational characteristic it is nowadays specified by CSS in the Flow Layout. A Block-level element occupies the entire horizontal space of its parent element (container), and vertical space equal to the height of its contents, thereby creating a "block". In this article, we'll examine HTML block-level elements and how they differ from inline-level elements.
Browsers typically display the block-level element with a newline both before and after the element. You can visualize them as a stack of boxes.
A block-level element always starts on a new line and takes up the full width available (stretches out to the left and right as far as it can).
The following example demonstrates the block-level element's influence:
Block-level elements
HTML
<p>This paragraph is a block-level element; its background has been colored to display the paragraph's parent element.</p>CSS
p { background-color: #8ABB55; }
Usage
- Block-level elements may appear only within a
<body>element.
Block-level vs. inline
There are a couple of key differences between block-level elements and inline elements:
- Content model
- Generally, block-level elements may contain inline elements and (sometimes) other block-level elements. Inherent in this structural distinction is the idea that block elements create "larger" structures than inline elements.
- Default formatting
- By default, block-level elements begin on new lines, but inline elements can start anywhere in a line.
The distinction of block-level vs. inline elements was used in HTML specifications up to 4.01. In HTML5, this binary distinction is replaced with a more complex set of content categories. While the "inline" category roughly corresponds to the category of phrasing content, the "block-level" category doesn't directly correspond to any HTML5 content category, but "block-level" and "inline" elements combined together correspond to the flow content in HTML5. There are also additional categories, e.g. interactive content.
Elements
The following is a complete list of all HTML "block-level" elements (although "block-level" is not technically defined for elements that are new in HTML5).
<address>- Contact information.
<article>- Article content.
<aside>- Aside content.
<blockquote>- Long ("block") quotation.
<details>- Disclosure widget.
<dialog>- Dialog box.
<dd>- Describes a term in a description list.
<div>- Document division.
<dl>- Description list.
<dt>- Description list term.
<fieldset>- Field set label.
<figcaption>- Figure caption.
<figure>- Groups media content with a caption (see
<figcaption>). <footer>- Section or page footer.
<form>- Input form.
<h1>,<h2>,<h3>,<h4>,<h5>,<h6>- Heading levels 1-6.
<header>- Section or page header.
<hgroup>- Groups header information.
<hr>- Horizontal rule (dividing line).
<li>- List item.
<main>- Contains the central content unique to this document.
<nav>- Contains navigation links.
<ol>- Ordered list.
<p>- Paragraph.
<pre>- Preformatted text.
<section>- Section of a web page.
<table>- Table.
<ul>- Unordered list.
See also
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