As the versions of HTML and XHTML have developed, quite a lot of markup has been deprecated, which means it has either already been removed from XHTML specifications or that it will be removed in coming versions. While you will still be able to use much of this markup with Transitional XHTML, Strict XHTML 1.0 has already removed most of the elements, attributes, and styles that you can read about in this appendix.
I have included it in this book, despite the fact that the markup is deprecated or out-of-date, because you are likely to come across it in other people's code, and on very rare occasions you might need to resort to some of it in order to get a specific job done (for example, if it has to work in very old browsers such as IE 3 and Netscape 3), and some of these browsers will not support what you want to do with CSS.
In addition to deprecated markup, you will also see some of the browser-specific markup that you may well come across. This is markup that Microsoft or Netscape (and in some cases both companies) added to its browsers to allow users to do more things than its competitors—but these elements and attributes never made it into the HTML recommendations, and are therefore referred to as browser-specific markup.
So not only does this Appendix Help you deal with markup you come across that has been deprecated, but you might also use some techniques to get the result you want. This Appendix Covers the following: