The Ajax Client
Introduction to XHTML
Welcome to the world of opportunity created by the World Wide Web. The Internet is almost four decades old, but it wasn’t until the web’s growth in popularity in the 1990s and the recent start of the Web 2.0 era that the explosion of opportunity we are experienc-ing began. Exciting new developments occur almost daily—the pace of innovation is un-precedented. In this chapter, you’ll develop your own web pages. As the book proceeds, you’ll create increasingly appealing and powerful web pages. Later in the book, you’ll learn how to create complete web-based applications with databases and user interfaces.
This chapter begins unlocking the power of web-based application development with XHTML—the Extensible HyperText Markup Language. Later in the chapter, we intro-duce more sophisticated XHTML techniques such as internal linking for easier page nav-igation, forms for collecting information from a web-page visitor and tables, which are particularly useful for structuring information from databases (i.e., software that stores structured sets of data). In the next chapter, we discuss a technology called Cascading Style Sheets™ (CSS), a technology that makes web pages more visually appealing.
Unlike procedural programming languages such as C, C++, or Java, XHTML is a markup language that specifies the format of the text that is displayed in a web browser such as Microsoft’s Internet Explorer or Mozilla Firefox.
One key issue when using XHTML is the separation of the presentation of a docu-ment (i.e., the document’s appearance when rendered by a browser) from the structure of the document’s information. XHTML is based on HTML (HyperText Markup Lan-guage)—a legacy technology of the World Wide Web Consortium (W3C). In HTML, it was common to specify both the document’s structure and its formatting. Formatting might specify where the browser placed an element in a web page or the fonts and colors used to display an element. The XHTML 1.0 Strict recommendation (the version of XHTML that we use in this book) allows only a document’s structure to appear in a valid XHTML document, and not its formatting. Normally, such formatting is specified with Cascading Style Sheets (Chapter 5). All our examples in this chapter are based upon the XHTML 1.0 Strict Recommendation.
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