Detailed explanation of HTML <meta> tag-HTML Tutorial-php.cn

Detailed explanation of HTML tag

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Release： 2017-03-25 11:46:42

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All browsers support the tag.

Definition and usage

element can provide meta-information about the page, such as description and keywords for search engines and update frequency. The

tag is located at the head of the document and does not contain any content. The tag's properties define the name/value pairs associated with the document.

Differences between HTML and XHTML

In HTML, the tag does not have a closing tag.

In XHTML, the tag must be closed properly.

Tips and Notes:

Note: The tag is always located inside the head element.

Note: Metadata is always passed in name/value pairs.

Required attributes

Attributes	Value	Description
content	some_text	Define meta-information related to the http-equiv or name attribute

Optional attributes

Attributes	Value	Description
http-equiv	content-type expires refresh set-cookie	Associate the content attribute to the HTTP header.
name	author description keywords generator revised others	Associate the content attribute to a name.
scheme	some_text	Define the format used to translate the content attribute value.

name attribute

The name attribute provides the name in a name/value pair. Neither HTML nor XHTML tags specify any predefined names. In general, you are free to use names that are meaningful to you and to readers of the source document.

"keywords" is a frequently used name. It defines a set of keywords for the document. Some search engines use these keywords to classify documents when they encounter them.

A meta tag like this may be helpful for getting indexed by search engines:

<meta name="keywords" content="HTML,ASP,PHP,SQL">

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If the name attribute is not provided, the name in the name/value pair will use the value of the http-equiv attribute .

http-equiv attribute

The http-equiv attribute provides a name for a name/value pair. and instructs the server to include name/value pairs in the header of the MIME document to be sent to the browser before sending the actual document.

When the server sends a document to the browser, it first sends a number of name/value pairs. Although some servers send many of these name/value pairs, all servers send at least one: content-type:text/html. This tells the browser to prepare to accept an HTML document.

When using the tag with the http-equiv attribute, the server will add the name/value pair to the content header sent to the browser. For example, add:

<meta http-equiv="charset" content="iso-8859-1">
<meta http-equiv="expires" content="31 Dec 2008">

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so that the header sent to the browser should contain:

content-type: text/html
charset:iso-8859-1
expires:31 Dec 2008

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Of course, only browsers can accept these additional header fields and use them in an appropriate manner. These fields only make sense when you use them.

content property

The content property provides the value in a name/value pair. The value can be any valid string.

The content attribute should always be used together with the name attribute or the http-equiv attribute.

scheme attribute

The scheme attribute is used to specify the scheme to be used to translate the attribute value. This scheme should be defined in the profile specified by the profile attribute of the tag.

Redirect This example demonstrates: redirecting the user to another address when the URL has changed.

<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<meta http-equiv="Refresh" content="5;url=http://www.w3school.com.cn" />
</head>
<body>
<p>
对不起。我们已经搬家了。您的 URL 是 <a href="http://www.w3school.com.cn">http://www.w3school.com.cn</a>
</p>
<p>您将在 5 秒内被重定向到新的地址。</p>
<p>如果超过 5 秒后您仍然看到本消息，请点击上面的链接。</p>
</body>
</html>

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