All About XHTML and XML
HTML is a great programming language for beginners to be able to wade in and make their own Web pages to be viewed on a computer. However, XML and XHTML, which are slightly more complicated, are both ways to describe web pages to other types of machines, like mobile phones, that can also browse the Internet and may not always understand HTML.
XML stands for extensible markup language, and actually encompasses a whole family of languages, including XHTML. According to Wikipedia, it is now used in most word processing software that emphasizes portability and accessibility across the Web, such as Microsoft Office, Open Office, and iWork.
According to w3schools.com, XHTML was invented to bridge the gap between HTML and XML. It is "cleaner" and more standardized than HTML, and can interact with a wider range of devices. However, this also means it has less room for programmer error.
If you want to learn to write code in XHTML, there are many available, free tutorials, including the previously mentioned one at w3schools.com. This will teach you the differences between coding in HTML and coding in XHTML, as well as proper XHTML syntax (things like using all lower case letters and, when appropriate, quotation marks within your tags) and how to validate your XHTML code by the standards of the World Wide Web Consortium, or W3C.
There are also quirkier guides to XHTML out there. The Free Software Magazine (FSM) brings you "Learning XHTML: Monty Python Style." Here, you can learn such information as what software to code your XHTML in, ways to practice your XHTML skills, and how to display a range of colors on your XHTML site, with plenty of "Monty Python and the Holy Grail" references sprinkled throughout.
XML newbies, meanwhile, can turn to the XML tutorial at tizag.com. It will teach you important concepts like the XML family tree structure, which shows how different parts of the document you are creating relate to one another as descendants, ancestors, children, siblings, and parents.
Another XML tutorial is available through webucator. Their free tutorial shows you how to create a simple, well-formed XML document. For more detailed XML knowledge, you may have to turn to the instructor-led services available on their site
Having knowledge of XHTML and XML in your inventory, in addition to HTML and Web design skills, will make you an even more in-demand property. Good luck and happy coding!