Web Design in a Nutshell, 3rd Edition

Document Structure and Inheritance

XML, XHTML, and HTML documents have an implicit structure or hierarchy. For instance, the html root element usually contains a head and a body, and the body, in turn, contains some number of block-level elements, such as paragraphs (p). A paragraph may include inline elements such as anchors (a) or emphasized text (em). This hierarchy can be visualized as a tree, branching out from the root. Figure 16-2 shows the document tree structure of a very simple XHTML document.

Figure 16-2. Document tree structure