Meta tags

Meta elements are tags used in HTML and XHTML documents to provide structured metadata about a Web page. They are part of a web page's head section. Multiple Meta elements with different attributes can be used on the same page. Meta elements can be used to specify page description, keywords and any other metadata not provided through the other head elements and attributes.

The meta element has two uses: either to emulate the use of an HTTP response header field, or to embed additional metadata within the HTML document.

With HTML up to and including HTML 4.01 and XHTML, there were four valid attributes: content, http-equiv, name and scheme. Under HTML 5 there are now five valid attributes, charset having been added. http-equiv is used to emulate an HTTP header, and name to embed metadata. The value of the statement, in either case, is contained in the content attribute, which is the only required attribute unless charset is given. charset is used to indicate the character set of the document, and is available in HTML5.

Such elements must be placed as tags in the head section of an HTML or XHTML document.

meta elements can specify headers which should be sent before the actual content when the HTML page is served from the web server to the client. For example:

as an alternative to the response header Content-Type: to indicate the media type and, more commonly needed, the UTF-8 character encoding.

Meta tags can be used to describe the contents of the page:

In this example, the meta element describes the contents of a web page.

Meta elements provide information about the web page, which can be used by search engines to help categorize the page correctly.

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Wikipedia