It specifies the document character set, which determines a character repertoire that contains all character s that occur in all text entities in the document, and the character numbers associated with those character s. The SGML declaration also specifies the syntax character set of the document, and a few other parameters that bind the abstract syntax of SGML to a concrete syntax. This concrete syntax determines how each text entity is mapped to a sequence of terminals in the grammar of the prologue. An HTML user agent should use the SGML declaration is given in section SGML Declaration for HTML . This section is only a summary.
Some markup also maps to data character strings.
Numeric character references also map to single- character strings, via the document character set. Each reference to one of the general entities defined in the HTML DTD also maps to a single- character string. Tags Tag s delimit element s such as headings, paragraphs, lists, character highlighting and links. Most HTML element s are identified in a document as a start tag , which gives the element name and attributes, followed by the content, followed by the end tag . Some element s only have a start tag without an end tag .