From http://www.w3schools.com (Copyright Refsnes Data)

HTML <meta> tag

Example

Describe metadata within an HTML document:

Metadata is information about data.

The <meta> tag provides metadata about the HTML document. Metadata will not be displayed on the page, but will be machine parsable.

Meta elements are typically used to specify page description, keywords, author of the document, last modified, and other metadata.

The <meta> tag always goes inside the head element.

The metadata can be used by browsers (how to display content or reload page), search engines (keywords), or other web services.

The <meta> tag is supported in all major browsers.

In HTML the <meta> tag has no end tag.

In XHTML the <meta> tag must be properly closed.

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

DTD indicates in which DTD the attribute is allowed. S=Strict, T=Transitional, and F=Frameset.

Attribute	Value	Description	DTD
content	text	Specifies the content of the meta information	STF

Attribute	Value	Description	DTD
http-equiv	content-type content-style-type expires refresh set-cookie	Provides an HTTP header for the information in the content attribute	STF
name	author description keywords generator revised others	Provides a name for the information in the content attribute	STF
scheme	format/URI	Specifies a scheme to be used to interpret the value of the content attribute	STF

dir, lang, xml:lang

For a full description, go to Standard Attributes.