eXtensible HyperText Markup Language (XHTML)

eXtensible HyperText Markup Language (XHTML), is a markup language, expression and Hypertext Markup Language (HTML) similar to, but the syntax is more strict. Speaking from the inheritance, HTML is based on Standard Generalized Markup Language (SGML) application, is a very flexible markup language, XHTML is based on Extensible Markup Language (XML), XML is an SGML subset. XHTML 1.0 in January 26, 2000 a W3C Recommendation.
XHTML is The Extensible HyperText Markup Language (extensible hypertext markup language) acronym. WEB HTML is a basic web page design language, XHTML is an XML-based markup language, it seems some resemblance with the HTML, only some small but important differences, XHTML is a playing a role similar to HTML, XML, So, essentially, XHTML is a transitional technology, combined with some of the power of XML and a simple majority of HTML features.
 The end of 2000, the International Organization W3C (World Wide Web Consortium) organization published the XHTML 1.0 version released. XHTML 1.0 HTML 4.0 is a basis in the optimization and improvement of the new language, the purpose of XML-based applications. XHTML is an increased of HTML, its scalability and flexibility to adapt to the future network applications will be more demand. Although the ability of powerful XML data conversion, can replace HTML, but in the face of thousands of existing sites based on HTML, design, direct use of XML is premature. Therefore, in HTML4.0 based on XML rules with its expansion, has been XHTML. Therefore, the purpose of establishing XHTML HTML to XML is to achieve the transition. Current international respected in the WEB site design is based on XHTML application of standards (known as CSS + DIV).
XHTML is the successor to the current HTML version. HTML syntax requires loose, so that authors of web pages for more convenient, but for machines, the syntax of the language more loosely to handle it more difficult for traditional computers, have the ability to loosely compatible syntax, but For many other devices, such as mobile phones, the difficulty is relatively large. The resulting DTD defined by the rules of grammar require more stringent XHTML.
 Most popular browsers can correctly parse XHTML, even if a little older browser, XHTML as a subset of HTML, and many can be resolved. In other words, almost all Web browsers parse HTML in the right, while compatible with XHTML. Of course, from the HTML completely transferred to XHTML, but also requires a process.
 With CSS (Cascading Style Sheets, Cascading Style Sheets) combined, XHTML can play the real power; This allows to achieve the separation of style with the same content, but also an organic combination of web code, in another separate file, you can also Mixing a variety of XML applications, such as MathML, SVG. 
 The transition from HTML to XHTML change is relatively small, mainly to meet the XML. The biggest change is that the document is required to be, and all tags must be closed, that is the end of the start tag of a corresponding label. In addition, XHTML all tags must be lowercase. HTML 2.0 has been in accordance with tradition, many people are the label capital, this significant difference between the two. In XHTML, all the parameter values, including figures, must be enclosed in double quotes (as in SGML and HTML, the quotes are not necessary, if the content is only numbers, letters and other special characters allowed, you can not quotes). " style="BACKGROUND-COLOR: #fff" onmouseout="this.style.backgroundColor='#fff'">All elements, including empty elements, such as img, br, also have to be closed, implemented in a way is to add backslash at the end of the opening tag, such as <code> <nowiki> <img… /> </ nowiki> </ code> 。" onmouseout="this.style.backgroundColor='#fff'">, <code> <nowiki> </ nowiki> </ code>. 。' style="BACKGROUND-COLOR: #fff" onmouseout="this.style.backgroundColor='#fff'">Parameter is omitted, it is not allowed, must <code> <nowiki> <option selected="selected"/> </ nowiki> </ code>. Detailed differences between the two, through [http://www.w3.org/TR/xhtml1/ # diffs W3C XHTML Help] to view it.