XHTML (Xtensible HyperText Markup Language) is a new generation of markup language which was created after HTML 4.1. According to W3C (World Wide Web Consortium), XHML is a “reformulation of HTML 4 in XML 1.0” which is specified within their manual on the markup language (http://www.w3.org/TR/xhtml1/).

The XML based markup language does contain the same set of attributes and element types as HTML 4.0. The two markup languages are very similar; however there are a few minor differences.
The main alterations that would make XHTML an improved markup to HTML:

• XHTML is easier to maintain
• XHTML is a more widley accepted in portable devices such as mobile phones or PDAs.
• XHTML is extensible (new tags can be added without a new document type declaration (DTD or DOCTYPE) being created
• XHMTL requires values or attributes must be within single quotes(‘) or double quotes (“).
• XHML requires tags to be properly nested
• XHML requires tags to always be closed
• XHML requires all tags to be specified in lowercase