David Yul
XHTML means: Extensible Hypertext Markup Language. XHTML can be viewed as the next step beyond HTML 4.0. Instead of calling it a HTML 5.0, the W3C has called it XHTML 1.0. The X in XHTML stand for EXTENSIBLE, according to the book, it means that outhors can customize their code by creating specialized tags and attributes to accomplish their goals. And the tool for creating these custom elements is the technology known as Cascading Style Sheets (CSS).
In XHTML you must use only the lowercase letters, and make sure you close all tags in the document,
There are three different types of pages of XHTML, these are: Strict page, Transitional page, and Frameset page, with these pages, you can identified which page you are writing by using !doctype tag.
Doctype tag is a tag that you can use in the XHTML to define the xhtml pages you are writing, and the version of Xhtml you are using.