The Meta element is an extensible mechanism for use in identifying
specialized document meta-information. Each Meta element occurrence specifies a
Name/Value pair. If multiple Meta elements are specified with the same
name, their combined CONTENT sections should be concatenated as a comma
separated list to be associated with the common NAME value.
This attribute binds the Meta CONTENT element to an HTTP header
field. When a browser requests a particular page containing a META
HTTP-Equiv element from a server, the CONTENT portion of the element
will be attached to the document header that is passed to the browser
before the rest of the actual document content. The browser or HTTP
server may use this information to process the document. Values are
not case sensitive.
Must begin with a letter ([A-Za-z]), followed by any number of characters in [A-Za-z0-9-_:.]