With HTML up to and including HTML 4.01 and XHTML, there were four valid attributes: codice_3, codice_4, codice_5 and codice_6. Under HTML 5 there are now five valid attributes, codice_7 having been added. codice_4 is used to emulate an HTTP header, and codice_5 to embed metadata. The value of the statement, in either case, is contained in the codice_3 attribute, which is the only required attribute unless codice_7 is given. codice_7 is used to indicate the character set of the document, and is available in HTML5.