HTML Elements-优快云博客

本文链接：https://blog.youkuaiyun.com/happysunray/article/details/83668768

本文详细介绍了HTML文档的构成，包括HTML元素的定义、语法结构、空元素的闭合方式及属性等内容，并通过实例展示了不同类型的HTML元素如何组合形成完整的HTML文档。

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HTML documents are defined by HTML elements.

HTML Elements

An HTML element is everything from the start tag to the end tag:

Start tag *	Element content	End tag *
<p>	This is a paragraph	</p>
<a href="default.htm" >	This is a link	</a>
<br />

* The start tag is often called the opening tag. The end tag is often called the closing tag.

HTML Element Syntax

An HTML element starts with a start tag / opening tag
An HTML element ends with an end tag / closing tag
The element content is everything between the start and the end tag
Some HTML elements have empty content
Empty elements are closed in the start tag
Most HTML elements can have attributes

Tip: You will learn about attributes in the next chapter of this tutorial.

Nested HTML Elements

Most HTML elements can be nested (can contain other HTML elements).

HTML documents consist of nested HTML elements.

HTML Document Example

<html>

<body>
<p>This is my first paragraph.</p>
</body>

</html>

The example above contains 3 HTML elements.

HTML Example Explained

The element:

<p>This is my first paragraph.</p>

The element defines a paragraph in the HTML document.
The element has a start tag and an end tag .
The element content is: This is my first paragraph.

The <body> element:

<body>
<p>This is my first paragraph.</p>
</body>

The <body> element defines the body of the HTML document.
The element has a start tag <body> and an end tag </body>.
The element content is another HTML element (a p element).

The <html> element:

<html>

<body>
<p>This is my first paragraph.</p>
</body>

</html>

The <html> element defines the whole HTML document.
The element has a start tag <html> and an end tag </html>.
The element content is another HTML element (the body element).

Don't Forget the End Tag

Most browsers will display HTML correctly even if you forget the end tag:

<p>This is a paragraph
<p>This is a paragraph

The example above will work in most browsers, but don't rely on it. Forgetting the end tag can produce unexpected results or errors.

Note: Future version of HTML will not allow you to skip end tags.

Empty HTML Elements

HTML elements with no content are called empty elements. Empty elements can be closed in the start tag.

is an empty element without a closing tag (the tag defines a line break).

In XHTML, XML, and future versions of HTML, all elements must be closed.

Adding a slash to the start tag, like , is the proper way of closing empty elements, accepted by HTML, XHTML and XML.

Even if works in all browsers, writing instead is more future proof.

HTML Tip: Use Lowercase Tags

HTML tags are not case sensitive: means the same as . Many web sites use uppercase HTML tags.

W3Schools use lowercase tags because the World Wide Web Consortium (W3C)recommends lowercase in HTML 4, and demands lowercase tags in future versions of (X)HTML.