What Do I need to Know about XHTML?
HyperText Markup Language (HTML) is used to create web pages. Web browsers read the HTML code of a particular page to render that page into a form visibly pleasing to users. The great advantage of HTML is it does not have to be compiled and is readable by people with no technical background. HTML has gone through several revisions over the years. In 2000 HTML 4 was reformulated into an eXtensible Markup Language (XML) 1.0 application, eXtensible HyperText Markup Language (XHTML). Understanding how XHTML works means understanding what XML does.
XML is simply a descriptive language used to store information. Unlike HTML, XML tags are not predefined. HTML tags have no meaning within XML. A note written in XML would use self-explanatory tags, which mean nothing within the context of HTML. XML is designed to store and transport data, while HTML is designed to display data. XML files are useful for displaying dynamic data on a web page. Using JavaScript, a designer can read the data contained in external XML files and update the data displayed on the page.
XHTML has different requirements than regular HTML. In particular, XHTML does not tolerate "bad" HTML, where tags are not closed properly or elements left vague and undefined. The explosion of Web browser software has meant that different display technologies will not recognize bad HTML coding. XHTML is designed to eliminate this problem by making the language cleaner and much more precise.
The markup tags in HTML must be nested and closed properly. They must also be in lower case and have no more than one root element. Every set of XHTML tags must be contained within an HTML tag, which is the root element used in XHTML. Child elements must be in pairs and nested properly within the parent element. Take the bold and italic tags, for instance. Whichever is used first, the corresponding closing tag must be used. If bold was used first and italic second, the italic closing tag must be used first and the bold closing tag second.
XHTML makes Web design easier because of the greater capabilities it offers. In practice, it works just like HTML except the XML application allows it to be much more effective. XHTML is used by the top hosting providers on the Internet, making it essential for maintaining a competitive edge.
