Sunday, November 1, 2009

Difference between HTML and XHTML

XHTML stands for Extensible HyperText Markup Language. It is a cleaner and stricter version of HTML, also more stable, sharpened and sophisticated version. XHTML, is a combination of XML (Extensible Markup Language) and HTML. XML is designed to describe data, while HTML is designed to display data.

HTML (the original language of World Wide Web) is rapidly being replaced by XHTML. XHTML is similar in most features to HTML due to the fact that XHTML was derived from HTML just to conform with XML standards. There are only a few minor differences between these two markup language, its only that XHTML is designed for being a HTML successor or some call it a better HTML.
  • One of the XHTML benefit is that it is more accepted in non “computer” devices such as cell phones, palm devices and other scaled down browsers.
  • All elements and attributes in XHTML documents have to be written in lower case (while it is not necessarily in HTML).
  • All opening tags must be closed with closing tags, in HTML many of these tags were left open and you still can view them in a browser without errors. Items like line breaks or images which are without HTML closing tags should have XHTML self-closing.
  • In XHTML, all the tags also have to be properly nested, it means that if you start tag “a” and open another tag within tag “a”, you have to close the latest tag first and then close tag “a” at the last. Although nesting is also followed in HTML but it is not as strict as in XHTML.
  • All values for attributes must be encased in double or single quotes and the attributes themselves should not be abbreviated.
  • The image tags should be provided with alt attributes which contain the image description in order to allow them have some requirements for accessibility along with different web standard.
  • Another XHTML only requirement is the declaration of the DOCTYPE which determines what rules your document will follow, which it inherited from XML. The first line you will see when you switch your XHTML page to the source code is a document type declaration (also called DTD or DOCTYPE) at the top of your XHTML documents. Most web pages being created today will include a doctype declaration. There are 3 DTDs for XHTML: Strict (only will validate if it is without deprecated tags), Transitional (will still validate with deprecated tags), and Frameset (for a page that “sets” up “frames”). All XHTML documents have to conform to the XML syntax rules.
XHTML is a more forward language that has been created to be compatible with both new and upcoming technology, and it is far more versatile than standard HTML is.

Part 1: HTML Part 2: HTML Attributes Part 3: HTML Table Part 4: Colspan and Rowspan

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