In this appendix, we introduce XHTMLthe Extensible HyperText Markup Language for creating Web content. Unlike procedural programming languages such as C, Fortran, Cobol and Visual Basic, XHTML is a markup language that specifies the format of text that is displayed in a Web browser, such as Microsoft's Internet Explorer or Netscape's Communicator.
 XHTML has replaced the HyperText Markup Language (HTML) as the primary means of describing Web content. XHTML provides more robust, richer and more extensible features than HTML. For more on XHTML/HTML, visit www.w3.org/markup.
One key issue when using XHTML is the separation of the presentation of a document (i.e., the document's appearance when rendered by a browser) from the structure of the document's information. Throughout this appendix, we will discuss this issue in depth.
In this appendix, we build several complete Web pages featuring text, hyperlinks, images, horizontal rules and line breaks. We also discuss more substantial XHTML features, including presentation of information in tables and incorporating forms for collecting information from a Web-page visitor. By the end of this appendix, you will be familiar with the most commonly used XHTML features and will be able to create more complex Web documents. In this appendix, we do not present any C++ programming.