The basic syntax and semantics of HTML are defined in the HTML standard, now in its final version, 4.01. HTML matured quickly, in barely a decade. At one time, a new version would appear before you had a chance to finish reading an earlier edition of this book. Today, HTML has stopped evolving. As far as the W3C is concerned, XHTML has taken over. Now the wait is for browser manufacturers to implement the standards.
The XHTML standard currently is version 1.0. Fortunately, XHTML version 1.0 is, for the most part, a reconstitution of HTML version 4.01. There are some differences. The popular browsers continue to support HTML documents, so there is no cause to stampede to XHTML. Do, however, start walking in that direction: a newer XHTML version, 2.0, is under consideration at the W3C, and browser developers are slowly but surely dropping nonstandard HTML features from their products.
Obviously, browser developers rely upon standards and accepted conventions to have their software properly format and display common HTML and XHTML documents. Authors use the standards to make sure they are writing effective, correct documents that get displayed properly by the browsers.
However, standards are not always explicit; manufacturers have some leeway in how their browsers might display an element. And to complicate matters, commercial forces have pushed developers to add into their browsers nonstandard extensions meant to improve the language.
Confused? Don’t be: in this book, we explore in detail the syntax, semantics, and idioms of the HTML version 4.01 and XHTML version 1.0 languages, along with the many important extensions that are supported in the latest versions of the most popular browsers.