The first set of tags beyond the tag, and , indicates the start and end of an HTML document. This set of tags contains all of the content of the Web page, the tags that format that content, and the tags that define the different parts of the document. Software tools, such as browsers, use these tags to determine where the HTML code in a file begins and ends. (Quelle: HTML: Comprehensive Concepts and Techniques , Fifth Edition, Gary B. Shelly, u.a., Course Technology Verlag, ISBN: 978-1-4239-2722-8, Defining the HTML Document, Chapter 2, Seite 35 f.)