Web Page Building Blocks
While Web pages have become increasingly complex, their underlying structure remains remarkably simple. A Web page is made up of three principal components: text content, the actual headers and paragraphs that appear on the page; occasional references to more complex content like links, images, and perhaps Flash animations; and markupinstructions that describe how the content and references should be displayed. It is important to note that each of these components is comprised exclusively of text. This essential feature means that Web pages can be saved in text-only format and viewed on practically any browser on any platform. It guarantees the universality of the Web.
Web pages also include information about the language or script in which the text was written (the encoding) as well as the kind of markup that describes it (doctype).
I will devote this chapter to explaining each of these important concepts.
Note: As I mentioned in the introduction, I use (X)HTML to refer to both HTML 4 and XHTML 1.0 in situations where they have identical properties, as in "(X)HTML's table element". On the other hand, for those instances in which I'm highlighting special characteristics unique to one or the other, I will use their individual names: "XHTML requires quotation marks around attribute values." For more details, consult How This Book Works on page 23.