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 .
The content of an element is a sequence of data character strings and nested element s. Some element s, such as anchors, cannot be nested. Anchors and character highlighting may be put inside other constructs. See the HTML DTD , section HTML DTD for full details. Element names are not case sensitive, but entity names are.