There is a hidden standard behind almost everything that we see and do when surfing the web, the HyperText Markup Language, short: HTML. Whether we look for information on Wikipedia, search for sites on Google, check our bank account, or become social on Twitter, Facebook, and YouTube—when we use a browser—we use HTML.

HTML is a language for presenting content on the Web that was first proposed by Tim Berners-Lee (1989). The standard has continuously evolved since the initial introduction, the most recent incarnation is HTML5 that is being developed by the World Wide Web Consortium (W3C) and the Web Hypertext Application Technology Working Group (WHATWG).1 Although each revision of HTML has established new features and restructured old ones, the basic grammar of HTML documents has not changed much over the years and is likely to remain fairly stable in the foreseeable future, making it one of the most important standards for working with and on the Web.

This chapter introduces the fundamentals of HTML from the perspective of a web data collector. We will learn how to use browsers to display the source code of webpages and inspect specific HTML elements (Section 2.1). Section 2.2 develops the logic of markup languages in general and the syntax of HTML as a specific instance of a markup language. We go on to present the most important vocabulary in HTML (Section 2.3). Finally, we consider parsing—the process of reconstructing the structure and semantics of HTML documents—and ...

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