As described in Chapter 17, both HyperText Markup Language (HTML) and eXtensible Markup Language (XML) are derived from the Standard Generalised Markup Language (SGML). In SGML, extra information is provided by means of ‘tags’, enabling SGML documents to be read by both machines and humans.


The tags provided within an HTML document are purely concerned with the way that the information in the document is presented (rendered, to use the technical term) by a web browser. HTML tags can be used to achieve a number of effects. As well as enabling basic text formatting, HTML tags can specify links, known as hypertext links, to other information both within the document and in other documents. They can also ...

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