Original Address: http://www.w3schools.com/xhtml/ 
  Translation: Fanweixiao 

  XHTML Tutorial 
  XHTML Guide 

  In this tutorial you will learn the difference between html and XHTML. You will also learn how this Web site was converted to XHTML. 
  In this guide, you can understand the different HTML and XHTML.    You can also learn how to convert this site is to XHTML standards. 

  Introduction To XHTML 
  XHTML entry 

  XHTML is a new, stricter and cleaner version of HTML. 
  XHTML is a new, stricter clean and is a version of HTML. 

  What Is XHTML? 
  What is XHTML? 
  XHTML stands for EXtensible EXtensible EXtensible HyperText HyperText Markup Markup Language Language 
  XHTML is aimed to replace HTML 
  XHTML is almost identical to HTML 4.01 
  XHTML is a stricter and cleaner version of HTML 
  XHTML is HTML defined as an XML application 
  XHTML is EXtensible EXtensible EXtensible HyperText HyperText Markup Markup Language Language (Extensible HTML) initials Its goal is to replace HTML 
  It is almost identical to HTML 4.01 compared to the HTML it is a strict, clean version of it is defined as HTML XML applications 

  What You Should Already Know 
  Before you continue you should have a Basic understanding of the following: 
  1.HTML and the basics of building Web pages 
  2.The basics of XML 
  You should already know: 
  As we continue to learn before you should have a knowledge of the following basic understanding: 
  1.HTML language and produced some of the basic Web-based Dongdong 
  2.XML the basis of knowledge 

  XHTML is the official HTML standard 

  XHTML 1.0 became an official w3c Recommendation January 26, 2000. 

  XHTML is the official standard HTML 
  XHTML 1.0 in the January 26, 2000 as the official recommendation of the W3C standards. 
  A W3C Recommendation means that the specification is stable, and that it has been reviewed by the W3C membership, and that the specification is now a Web standard. 
  W3C recommendation intended to regulate the stability it has been repeatedly revised to W3C group of the norms now become our standard network 

  W3C defines XHTML as the latest version of HTML. XHTML will gradually replace HTML. 
  W3C XHTML will be defined as the latest version of HTML, and it will gradually replace the HTML 

  All New Browsers Support XHTML 
  XHTML is compatible with HTML 4.01. 
  All new browsers have support for XHTML. 
  All new browsers support XHTML 
  XHTML and HTML4.01 is the same, so all the new browsers support it. 

  All new browsers support XHTML 
  XHTML and HTML4.01 is the same, so all the new browsers support it. 

  What You Should Already Know 
  Before you continue you should have a basic understanding of the following: 
  1.HTML and the basics of building Web pages 
  2.The basics of XML 
  You should already know: 
  As we continue to learn before you should have a knowledge of the following basic understanding: 
  1.HTML language and produced some of the basic Web-based Dongdong 
  2.XML the basis of knowledge 

  XHTML is the official HTML standard 

  XHTML 1.0 became an official W3C Recommendation January 26, 2000. 

  XHTML is the official standard HTML 
  XHTML 1.0 in the January 26, 2000 as the official recommendation of the W3C standards. 
  A W3C Recommendation means that the specification is stable, and that it has been reviewed by the W3C membership, and that the specification is now a Web standard. 
  W3C recommendation intended to regulate the stability it has been repeatedly revised to W3C group of the norms now become our standard network 

  W3C defines XHTML as the latest version of HTML. XHTML will gradually replace HTML. 
  W3C XHTML will be defined as the latest version of HTML, and it will gradually replace the HTML 

  All New Browsers Support XHTML 
  XHTML is compatible with HTML 4.01. 
  All new browsers have support for XHTML. 
  All new browsers support XHTML 
  XHTML and HTML4.01 is the same, so all the new browsers support it. 

  All new browsers support XHTML 
  XHTML and HTML4.01 is the same, so all the new browsers support it. 

  XHTML is a combination of HTML and XML (eXtensible Markup Language). 
  XHTML HTML and XML is an organic combination. 
  XHTML consists of all the elements in HTML 4.01 combined with the Syntax of XML. 
  HTML4.01 in all the elements of the syntax of XML and a combination of XHTML. 
  Why XHTML? 
  Why do we use XHTML? 
  We have reached a point where many pages on the WWW contain "bad" HTML. 
  Development of the Internet to now, there have been too many bad HTML pages. 
  The following HTML code will work fine if you view it in a browser, even if it does not follow the HTML rules: 
  Below these HTML code in your browser can be very good, even if it does not follow the HTML standard. 

<html>
<head>
  <title> This is bad HTML </ title> 
<body>
  <h1> Bad HTML 
  </ Body> 

  XML is a markup language where everything has to be marked up correctly, which results in "well-formed" documents. 
  XML is a markup language, must be everywhere all the right markings, and its inevitable result is a "good format" documents. 
  XML was designed to describe data and HTML was designed to Display data. 
  XML is designed to describe data, and the HTML is designed to display data 
  Today's market consists of different browser technologies, some browsers run internet on computers, and some browsers run internet on mobile phones and hand helds. The last-mentioned do not have the resources or power to interpret a "bad" markup language. 
  Now on the market there are many browser technology, which can run on a PC, there are some in the mobile phone or handheld computer running.    Finally, note that they have not enough resources to explain or to a "bad" markup language. 
  Therefore - by combining HTML and XML, and their strengths, we got a markup language that is useful now and in the future - XHTML. 
  Therefore, the adoption of HTML and XML organic combination, coupled with their respective strengths, we are now in the future and this was the perfect Markup Language - XHTML 
  XHTML pages can be read by all XML enabled devices AND while waiting for the rest of the world to upgrade to XML supported browsers, XHTML gives you the opportunity to write "well-formed" documents now, that work in all browsers and that are backward browser compatible! 
  When the world's other browsers have been upgraded to support the XML, XHTML XML can be all the support equipment read, write XHTML give you a "good format" documents opportunities in these documents can be around here Show-in, and a good backward compatibility. 

  You can prepare yourself for XHTML by starting to write strict HTML. 
  You can start writing HTML code to strict for your XHML to prepare for the road 

  How To Get Ready For XHTML 
  How do I begin XHTML? 
  XHTML is the next generation of HTML, but it will of course take some time before browsers and other software products are ready for it. 
  XHTML is the next generation of HTML language, of course, in the new browser and other related software products, before it can be delayed for a period of time universal. 
  In the meantime there are some important things you can do to prepare yourself for it. As you will learn from this tutorial, XHTML is not very different from HTML 4.01, so bringing your code up to 4.01 standards is a very good start. Our complete HTML 4.01 reference can help you with that. 
  Meanwhile, there are some important things you can do is to learn to prepare for it.    Just as you can learn from this guide to the same things, with HTML4.01 XHTML is not a lot different, so you rewrite the code-4.01 standard is a very good start, we complete reference can help you HTML4.01 solve this problem. 
  In addition, you should start NOW to write your HTML code in lowercase letters, and NEVER make the bad habit of skipping end tags like the </ p>. 
  In addition, you should now begin to use lowercase letters to write your HTML code, and never again, as before, as a Skip </ p> This marked the end of the bad habits. 
  Happy coding! 
  Among reveling in the coding! 

  The Most Important Differences: 
  The main difference between: 
  XHTML elements must be properly nested 
  XHTML documents must be well-formed 
  Tag names must be in lowercase 
  All XHTML elements must be closed 
  XHTML nested elements must be correct 
  XHTML document must be a good format must be marked with the name of lowercase letters about XHTML elements must have at closing 

  Elements Must Be Properly Nested 
  Elements (Marking) must be correct nested 
  In HTML some elements can be improperly nested within each other like this: 
  In HTML, some markers to the right mutual non-nested, like this: 

  <b> <i> This text is bold and italic </ b> </ i> 

  In XHTML all elements must be properly nested within each other like this: 
  XHTML in all of the markers must be correct nested like this: 
  <b> <i> This text is bold and italic </ i> </ b> 

  Note: A common mistake in nested lists, is to forget that the inside list must be within an li element, like this: 
  NOTE: nested in the list often when we committed a mistake, it is forgotten that inserted new list must be in a <li> tag, like this 
<ul>
  <li> Coffee </ li> 
  <li> Tea 
<ul>
  <li> Black tea </ li> 
  <li> Green tea </ li> 
  </ Ul> 
  <li> Milk </ li> 
  </ Ul> 

  This is correct: 
  Correct wording 
<ul>
  <li> Coffee </ li> 
  <li> Tea 
<ul>
  <li> Black tea </ li> 
  <li> Green tea </ li> 
  </ Ul> 
  </ Li> 
  <li> Milk </ li> 
  </ Ul> 

  Notice that we have inserted a </ li> tag after the </ ul> tag in the "correct" code example. 
  In the meantime correct code examples, we note that In "/ ul> after adding a </ li> marker? 

  Documents Must Be Well-formed 
  Documentation must be good format 
  All XHTML elements must be nested within the <html> root element. All other elements can have sub (children) elements. Sub elements must be in pairs and correctly nested within their parent element. The basic document structure is: 
  All XHTML must be labeled using nested In "html> root of the marker.    All other markings can have their own sub-marker.    Father marker in the marker of the pair must also be nested and the correct use.    The basic structure of a web page is this: 

<html>
  <head> ... </ Head> 
  <body> ... </ Body> 
  </ Html> 

  Tag Names Must Be In Lower Case 
  Name must be marked with lowercase letters 
  This is because XHTML documents are XML applications. XML is case-sensitive. Tags like <br> and <BR> are interpreted as different tags. 
  This is because the document is XHTML XML applications, XML is case sensitive, and as <br> <BR> will be considered for the two were not marked. 
  This is wrong: 
  Wrong: 
<BODY>
  <P> This is a paragraph </ P> 
  </ BODY> 

  This is correct: 
  Correct 

<body>
  <p> This is a paragraph </ p> 
  </ Body> 

  All XHTML Elements Must Be Closed 
  XHTML all the markings must have closed at 
  Non-empty elements must have an end tag. 
  Non-empty marker must have a closed at. 
  This is wrong: 
  This is a mistake: 

  <p> This is a paragraph 
  <p> This is another paragraph 

  This is correct: 
  This is correct 

  <p> This is a paragraph </ p> 
  <p> This is another paragraph </ p> 

  Empty Elements Must Also Be Closed 
  Air must also be marked at close 
  Empty elements must either have an end tag or the start tag must end with />. 
  Close air must be marked at the beginning or at add /> to end 
  This is wrong: 
  Wrong code 

  This is a break <br> 
  Here comes a horizontal rule: <hr> 
  Here's an image <img src="happy.gif" alt="Happy face"> 

  This is correct: 
  Correct: 

  This is a break <br /> 
  Here comes a horizontal rule: <hr /> 
  Here's an image <img src="happy.gif" alt="Happy face" /> 

  IMPORTANT Compatibility Note: 
  On the compatibility of important note: 
  To make your XHTML compatible with today's browsers, you should add an extra space before the "/" symbol like this: <br />, and this: <hr />. 
  In order to make your XHTML compatible with the existing browser, you must / symbol increase before a special spaces, like this: <br /> <hr /> 

  Writing XHTML demands a clean HTML syntax. 
  We need a clean syntax to write HTML pages XHTML 
  Some More XHTML Syntax Rules: 
  More XHTML syntax: 

  Attribute Names Must Be In Lower Case 
  Attribute names must use lowercase 

  This is wrong: 
  Error code: 
  <table WIDTH="100%"> 
  This is correct: 
  Correct code: 
  <table Width="100%"> 

  Attribute values Must Be Quoted 
  Attribute value must quote 

  This is wrong: 
  Error code: 
  <table Width=100%> 
  This is correct: 
  Correct code: 
  <table Width="100%"> 

  Attribute Minimization Is Forbidden 
  Attributes abbreviated method is prohibited 
  This is wrong: 

  <dl Compact> 
  <input Checked> 
  <input Readonly> 
  <input Disabled> 
  <option Selected> 
  <frame Noresize> 

  This is correct: 

  <dl Compact="compact"> 
  <input Checked="checked" /> 
  <input Readonly="readonly" /> 
  <input Disabled="disabled" /> 
  <option Selected="selected" /> 
  <frame Noresize="noresize" /> 

  Here is a list of the minimized attributes in HTML and how they should be written in XHTML: 
  In HTML abbreviated attributes and its XHTML in writing a list of what it should: 
  HTML XHTML 
  Compact compact = "compact" 
  Checked checked = "checked" 
  Declare declare = "declare" 
  Readonly readonly = "readonly" 
  Disabled disabled = "disabled" 
  Selected selected = "selected" 
  Defer defer = "defer" 
  Ismap ismap = "ismap" 
  Nohref nohref = "nohref" 
  Noshade noshade = "noshade" 
  Nowrap nowrap = "nowrap" 
  Multiple multiple = "multiple" 
  Noresize noresize = "noresize" 

  The id Attribute Replaces The name Attribute 
  Id attribute to the use of alternative name attribute 
  HTML 4.01 defines a name attribute for the elements a, applet, frame, iframe, img, and map. In XHTML the name attribute is deprecated. Use id instead. 
  For a, applet, frame, iframe, and map img, HTML 4.01 in the definition of a name attribute in XHTML is not in favour of doing so, to replace the use of id name. 
  This is wrong: 

  <img Src="picture.gif" name="picture1" /> 

  This is correct: 

  <img Src="picture.gif" id="picture1" /> 

  Note: To interoperate with older browsers for a while, you should use both name and id, with identical attribute values, like this: 
  Note: To version of the browser relatively low presence, you should also use name and id attributes, and they should be the value of the two is the same, like this: 
  <img Src="picture.gif" id="picture1" name="picture1" /> 

  The Lang Attribute 
  Lang attributes 
  The lang attribute applies to almost every XHTML element. It specifies the language of the content within an element. 
  Lang attributes can be applied to almost all of XHTML elements.    It designated elements of the contents of the language set. 
  If you use the lang attribute in an element, you must add the xml: lang attribute, like this: 
  If you like an Element in the application lang attributes, you must add xml: lang attribute, like this: 
  <div Lang="no" xml:lang="no"> Heia Norge! </ Div> 
  Mandatory XHTML Elements 
  Mandatory elements of XHTML 
  All XHTML documents must have a DOCTYPE declaration. The html, head and body elements must be present, and the title must be present inside the head element. 
  All XHTML documents must have a DOCTYPE reputation.    Html, head and body elements must appear, and title must appear in the head, 
  This is a minimum XHTML document template: 
  This is one of the least of XHTML document templates 
  <! DOCTYPE Doctype goes here> 
  <html Xmlns="http://www.w3.org/1999/xhtml"> 
<head>
  <title> Title goes here </ title> 
  </ Head> <body> 
  Body text goes here 
  </ Body> </ html> 
  Note: The DOCTYPE declaration is not a part of the XHTML document itself. It is not an XHTML element, and it should not have a closing tag. 
  NOTE: DOCTYPE statement is not part of their XHTML documents.    It is not XHTML elements, it has not closed at. 
  Note: The xmlns attribute inside the <html> tag is required in XHTML. However, the validator on w3.org does not complain when this attribute is missing in an XHTML document. This is because "xmlns = http://www.w3 .org/1999/xhtml "is a fixed value and will be added to the <html> tag even if you do not include it. 
  NOTE: XHTML files of the xmlns attribute appear in the html tags.    However, the effectiveness of inspection w3.org will not be on this property does not appear in your XHTML documents and reports errors.    This is because "xmlns = http://www.w3.org/1999/xhtml" is a fixed value, even if your file does not contain it, it will be automatically added. 
  You will learn more about the XHTML document type definition in the next chapter. 
  In the next chapter of the study, you will learn more XHTL document type definition of knowledge. 

  The XHTML standard defines three Document Type Definitions. 
  The most common is the XHTML Transitional. 
  XHTML standard definition of a document type definition of the three, which is the most common type definition transition XHTML 

  The <! DOCTYPE> Is Mandatory 
  <! DOCTYPE> marking is mandatory 
  An XHTML document consists of three main parts: 
  XHTML is a document by the following three main components consisting of 
  The DOCTYPE 
  The Head 
  The Body 

  The basic document structure is: 
  Basic structure of the document is: 
  <! DOCTYPE ...> 
<html>
<head>
  <title> ... </ Title> 
  </ Head> 
  <body> ... </ Body> 
  </ Html> 

  The DOCTYPE declaration should always be the first line in an XHTML document. 
  DOCTYPE statement should always appear in a document of the first line XHTML 

  An XHTML Example 
  An example of XHTML 
  This is a simple (minimal) XHTML document: 
  This is a simple example of XHTML documents 
  <! DOCTYPE html 
  PUBLIC "- / / W3C / / DTD XHTML 1.0 Strict / / EN" 
  "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 
<html>
<head>
  <title> Simple document </ title> 
  </ Head> 
<body>
  <p> A simple paragraph </ p> 
  </ Body> 
  </ Html> 

  The DOCTYPE declaration defines the document type: 
  DOCTYPE statement of the document type definition 
  <! DOCTYPE html 
  PUBLIC "- / / W3C / / DTD XHTML 1.0 Strict / / EN" 
  "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 

  The rest of the document looks like HTML: 
  Documentation remaining part looks more like the HTML 
<html>
<head>
  <title> Simple document </ title> 
  </ Head> 
<body>
  <p> A simple paragraph </ p> 
  </ Body> 
  </ Html> 

  The three Document Type Definitions 
  Three kinds of document type definition 
  1.DTD specifies the syntax of a web page in SGML. 
  2.DTD is used by SGML applications, such as HTML, to specify Rules that apply to the markup of documents of a particular type, including a set of element and entity declarations. 
  3.XHTML is specified in an SGML document type definition or 'DTD'. 
  4.An XHTML DTD describes in precise, computer-readable language the allowed syntax and grammar of XHTML markup. 
  1.DTD specified in SGML (Standard General Markup Language) pages of Grammar 
  2.DTD be used by SGML applications, such as HTML, in order to specify a particular type of document marking the rules, which includes an element of the statement and the entire entity set. 
  3.XHTML was designated in a document type or SGML DTD in the 
  4.XHTML DTD precise description of a computer can allow identification of the language syntax and XHTML marked grammar can be used. 
  There are currently three XHTML document types: 
  Three XHTML document types: 
STRICT
TRANSITIONAL
FRAMESET
  Strict framework of the transitional type of 

  XHTML 1.0 specifies three XML document types that correspond to three DTDs: Strict, Transitional, and Frameset. 
  XHTML 1.0 identified three types of XML documents to adapt to three DTD: strict type, and the framework of transition 

  Strict XHTML 1.0 
  Strictly - 
  <DOCTYPE html PUBLIC "- / / W3C / / DTD XHTML 1.0 Strict / / EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> Use this when you want really clean markup, free of presentational clutter. Use this together with Cascading style Sheets. 
  When you want to clean and clean marker to avoid the chaos of the performance, and put it to use CSS 

  XHTML 1.0 Transitional 
  Transition 
  <! DOCTYPE html 
  PUBLIC "- / / W3C / / DTD XHTML 1.0 Transitional / / EN" 
  "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 

  Use this when you need to take advantage of HTML's presentational features and when you want to support browsers that don't understand Cascading Style Sheets. 
  When you need to take full advantage of the performance of HTML features or when you wish to support those who do not support css browser when you can use the transition. 

  XHTML 1.0 Frameset 
  <! DOCTYPE html 
  PUBLIC "- / / W3C / / DTD XHTML 1.0 Frameset / / EN" 
  "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd"> 

  Use this when you want to use HTML Frames to partition the browser window into two or more frames. 
  When you use HTML framework of a browser window split into two or more time-use framework structure 

  (Reproduced Please specify the source) 

  The <! DOCTYPE> Is Mandatory 
  <! DOCTYPE> marking is mandatory 
  An XHTML document consists of three main parts: 
  XHTML is a document by the following three main components consisting of 
  The DOCTYPE 
  The Head 
  The Body 

  The basic document structure is: 
  Basic structure of the document is: 
  <! DOCTYPE ...> 
<html>
<head>
  <title> ... </ Title> 
  </ Head> 
  <body> ... </ Body> 
  </ Html> 

  The DOCTYPE declaration should always be the first line in an XHTML document. 
  DOCTYPE statement should always appear in a document of the first line XHTML 

  An XHTML Example 
  An example of XHTML 
  This is a simple (minimal) XHTML document: 
  This is a simple example of XHTML documents 
  <! DOCTYPE html 
  PUBLIC "- / / W3C / / DTD XHTML 1.0 Strict / / EN" 
  "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 
<html>
<head>
  <title> Simple document </ title> 
  </ Head> 
<body>
  <p> A simple paragraph </ p> 
  </ Body> 
  </ Html> 

  The DOCTYPE declaration defines the document type: 
  DOCTYPE statement of the document type definition 
  <! DOCTYPE html 
  PUBLIC "- / / W3C / / DTD XHTML 1.0 Strict / / EN" 
  "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 

  The rest of the document looks like HTML: 
  Documentation remaining part looks more like the HTML 
<html>
<head>
  <title> Simple document </ title> 
  </ Head> 
<body>
  <p> A simple paragraph </ p> 
  </ Body> 
  </ Html> 

  The three Document Type Definitions 
  Three kinds of document type definition 
  1.DTD specifies the syntax of a web page in SGML. 
  2.DTD is used by SGML applications, such as HTML, to specify rules that apply to the markup of documents of a particular type, including a set of element and entity declarations. 
  3.XHTML is specified in an SGML document type definition or 'DTD'. 
  4.An XHTML DTD describes in precise, computer-readable language the allowed syntax and grammar of XHTML markup. 
  1.DTD specified in SGML (Standard General Markup Language) pages of Grammar 
  2.DTD be used by SGML applications, such as HTML, in order to specify a particular type of document marking the rules, which includes an element of the statement and the entire entity set. 
  3.XHTML was designated in a document type or SGML DTD in the 
  4.XHTML DTD precise description of a computer can allow identification of the language syntax and XHTML marked grammar can be used. 
  There are currently three XHTML document types: 
  Three XHTML document types: 
STRICT
TRANSITIONAL
FRAMESET
  Strict framework of the transitional type of 

  XHTML 1.0 specifies three XML document types that correspond to three DTDs: Strict, Transitional, and Frameset. 
  XHTML 1.0 identified three types of XML documents to adapt to three DTD: strict type, and the framework of transition 

  Strict XHTML 1.0 
  Strictly - 
  <DOCTYPE html PUBLIC "- / / W3C / / DTD XHTML 1.0 Strict / / EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> Use this when you want really clean markup, free of presentational clutter. Use this together with Cascading Style Sheets. 
  When you want to clean and clean marker to avoid the chaos of the performance, and put it to use CSS 

  XHTML 1.0 Transitional 
  Transition 
  <! DOCTYPE html 
  PUBLIC "- / / W3C / / DTD XHTML 1.0 Transitional / / EN" 
  "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 

  Use this when you need to take advantage of HTML's presentational features and when you want to support browsers that don't understand Cascading Style Sheets. 
  When you need to take full advantage of the performance of HTML features or when you wish to support those who do not support CSS browser when you can use the transition. 

  XHTML 1.0 Frameset 
  <! DOCTYPE html 
  PUBLIC "- / / W3C / / DTD XHTML 1.0 Frameset / / EN" 
  "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd"> 

  Use this when you want to use HTML Frames to partition the browser window into two or more frames. 
  When you use HTML framework of a browser window split into two or more time-use framework structure 

  (Reproduced Please specify the source) 

  The <! DOCTYPE> Is Mandatory 
  <! DOCTYPE> marking is mandatory 
  An XHTML document consists of three main parts: 
  XHTML is a document by the following three main components consisting of 
  The DOCTYPE 
  The Head 
  The Body 

  The basic document structure is: 
  Basic structure of the document is: 
  <! DOCTYPE ...> 
<html>
<head>
  <title> ... </ Title> 
  </ Head> 
  <body> ... </ Body> 
  </ Html> 

  The DOCTYPE declaration should always be the first line in an XHTML document. 
  DOCTYPE statement should always appear in a document of the first line XHTML 

  An XHTML Example 
  An example of XHTML 
  This is a simple (minimal) XHTML document: 
  This is a simple example of XHTML documents 
  <! DOCTYPE html 
  PUBLIC "- / / W3C / / DTD XHTML 1.0 Strict / / EN" 
  "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 
<html>
<head>
  <title> Simple document </ title> 
  </ Head> 
<body>
  <p> A simple paragraph </ p> 
  </ Body> 
  </ Html> 

  The DOCTYPE declaration defines the document type: 
  DOCTYPE statement of the document type definition 
  <! DOCTYPE html 
  PUBLIC "- / / W3C / / DTD XHTML 1.0 Strict / / EN" 
  "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 

  The rest of the document looks like HTML: 
  Documentation remaining part looks more like the HTML 
<html>
<head>
  <title> Simple document </ title> 
  </ Head> 
<body>
  <p> A simple paragraph </ p> 
  </ Body> 
  </ Html> 

  The three Document Type Definitions 
  Three kinds of document type definition 
  1.DTD specifies the syntax of a web page in SGML. 
  2.DTD is used by SGML applications, such as HTML, to specify rules that apply to the markup of documents of a particular type, including a set of element and entity declarations. 
  3.XHTML is specified in an SGML document type definition or 'DTD'. 
  4.An XHTML DTD describes in precise, computer-readable language the allowed syntax and grammar of XHTML markup. 
  1.DTD specified in SGML (Standard General Markup Language) pages of Grammar 
  2.DTD be used by SGML applications, such as HTML, in order to specify a particular type of document marking the rules, which includes an element of the statement and the entire entity set. 
  3.XHTML was designated in a document type or SGML DTD in the 
  4.XHTML DTD precise description of a computer can allow identification of the language syntax and XHTML marked grammar can be used. 
  There are currently three XHTML document types: 
  Three XHTML document types: 
STRICT
TRANSITIONAL
FRAMESET
  Strict framework of the transitional type of 

  XHTML 1.0 specifies three XML document types that correspond to three DTDs: Strict, Transitional, and Frameset. 
  XHTML 1.0 identified three types of XML documents to adapt to three DTD: strict type, and the framework of transition 

  Strict XHTML 1.0 
  Strictly - 
  <DOCTYPE html PUBLIC "- / / W3C / / DTD XHTML 1.0 Strict / / EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> Use this when you want really clean markup, free of presentational clutter. Use this together with Cascading Style Sheets. 
  When you want to clean and clean marker to avoid the chaos of the performance, and put it to use CSS 

  XHTML 1.0 Transitional 
  Transition 
  <! DOCTYPE html 
  PUBLIC "- / / W3C / / DTD XHTML 1.0 Transitional / / EN" 
  "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 

  Use this when you need to take advantage of HTML's presentational features and when you want to support browsers that don't understand Cascading Style Sheets. 
  When you need to take full advantage of the performance of HTML features or when you wish to support those who do not support CSS browser when you can use the transition. 

  XHTML 1.0 Frameset 
  <! DOCTYPE html 
  PUBLIC "- / / W3C / / DTD XHTML 1.0 Frameset / / EN" 
  "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd"> 

  Use this when you want to use HTML Frames to partition the browser window into two or more frames. 
  When you use HTML framework of a browser window split into two or more time-use framework structure 

  XHTML HowTo 
  How can I convert the existing site XHTML? 
  To convert a Web site from HTML to XHTML, you should be familiar with the XHTML syntax rules of the previous chapters. The following steps were executed (in the order listed below): 
  HTML website will be a switch to XHTML, you should be familiar with the previous chapter XHTML syntax rules.    Below the content will help you. 

  A DOCTYPE Definition Was Added 
  The following DOCTYPE declaration was added as the first line of every page: 
  This will be the following lines of code added to the first line of each page. 

  <! DOCTYPE html PUBLIC 
  "- / / W3C / / DTD XHTML 1.0 Transitional / / EN" 
  "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 

  Note that we used the transitional DTD. We could have chosen the strict DTD, but found it a little too "strict", and a little too hard to conform to. 
  Attention, oh, here we use the transtitional DTD.    Of course, we can also choose Strict DTD, but we found it a bit too strict, in order to complete it too hard to follow. 

  A Note About The DOCTYPE 
  Your pages must have a DOCTYPE declaration if you want them to validate as correct XHTML. 
  If you want to make your pages to meet the effectiveness of the correct XHTML you must use a DOCTYPE statement. 
  Be aware however, that newer browsers (like Internet Explorer 6) might treat your document differently depending on the <! DOCTYPE> declaration. If the browser reads a document with a DOCTYPE, it might treat the document as "correct." Malformed XHTML might fall over and display differently than without a DOCTYPE. 
  But you must note, a relatively new browser (IE6 like) to see you in the pages of the DOCTYPE statement may have different treatment.    If your browser read a statement containing DOCTYPE pages, it might think that this page will be "correct."    If we do not use the abnormal DOCTYPE XHTML pages of the above elements may "fall down" and to the beginning of a different page. 
  Lower Case Tag And Attribute Names 
  Since XHTML is case sensitive, and since XHTML only accepts lower case HTML tags and attribute names, a general search and replace function was executed to replace all upper case tags with lowercase tags. The same was done for attribute names. We have always tried to use lower case names in our Web, so the replace function did not produce many real substitutions. 
  XHTML is case-sensitive, and only lowercase mark and attribute names, you can use the function to handle the replacement. 
  All Attributes Were Quoted 
  Since the W3C XHTML 1.0 Recommendation states that all attribute values must be quoted, every page in the web was checked to see that attributes values were properly quoted. This was a time-consuming job, and we will surely never again forget to put quotes around our attribute values. 
  Use brackets to attribute cause, there is no simple method, it is this amount of time spent on work, as long as do not forget to recall that after the brackets on the line. 

  Empty Tags: <hr>, <br> and <img> 
  Empty tags are not allowed in XHTML. The <hr> and <br> tags should be replaced with <hr /> and <br />. 

  This produced a problem with Netscape that misinterpreted the <br/> tags. We don't know why, but changing it to <br /> worked fine. After that discovery, a general search and replace function was executed to swap the tags. 

  A few other tags (like the <img> tag) were suffering from the same problem as above. We decided not to close the <img> tags with </ img>, but with /> at the end of the tag. This was done manually. 
  Had too wordy.    That is the mark just The Web Site Was Validated 
  After that, all pages were validated against the official w3c dtd with this link: XHTML Validator. A few more errors were found and edited manually. The most common error was missing </ li> tags in lists. 
  Your website can be official XHTML validity check to be verified with more errors will be detected and Border manual, and the most common mistake is to forget the list, write </ li> has. 
  Should we have used a converting tool? Well, we could have used TIDY. 
  TIDY can use the conversion tools 
  Dave Raggett's HTML TIDY is a free utility for cleaning up HTML code. It also works great on the hard-to-read markup generated by specialized HTML editors and conversion tools, and it can help you identify where you need to pay further attention on making your pages more accessible to people with disabilities. 
  Dave Raggett's HTML TIDY HTML is used to optimize the code free software, it can also good to deal with those from special HTML editors and conversion tool for the curious markings at the same time, it can help you who you must logo from a long-term attention to the angle of your pages can be used by people with disabilities? 
  The reason why we didn't use Tidy? We knew about XHTML when we started writing this web site. We knew that we had to use lowercase tag names and that we had to quote our attributes. So when the time came (to do the conversion), we simply had to test our pages against the W3C XHTML validator and correct the few mistakes. AND - we have learned a lot about writing "tidy" HTML code. 
  We do not use TIDY reason is that when we do this site when we know XHTML, lowercase and the quotes we know.    So when the time we need to be converted simply by the W3C XHTML validator of the few to rectify our mistakes.    And, we have to know how to write a clean HTML code. 

  A DOCTYPE Definition Was Added 
  The following DOCTYPE declaration was added as the first line of every page: 
  This will be the following lines of code added to the first line of each page. 

  <! DOCTYPE html PUBLIC 
  "- / / W3C / / DTD XHTML 1.0 Transitional / / EN" 
  "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 

  Note that we used the transitional DTD. We could have chosen the strict DTD, but found it a little too "strict", and a little too hard to conform to. 
  Attention, oh, here we use the transtitional DTD.    Of course, we can also choose Strict DTD, but we found it a bit too strict, in order to complete it too hard to follow. 

  A Note About The DOCTYPE 
  Your pages must have a DOCTYPE declaration if you want them to validate as correct XHTML. 
  If you want to make your pages to meet the effectiveness of the correct XHTML you must use a DOCTYPE statement. 
  Be aware however, that newer browsers (like Internet Explorer 6) might treat your document differently depending on the <! DOCTYPE> declaration. If the browser reads a document with a DOCTYPE, it might treat the document as "correct." Malformed XHTML might fall over and display differently than without a DOCTYPE. 
  But you must note, a relatively new browser (IE6 like) to see you in the pages of the DOCTYPE statement may have different treatment.    If your browser read a statement containing DOCTYPE pages, it might think that this page will be "correct."    If we do not use the abnormal DOCTYPE XHTML pages of the above elements may "fall down" and to the beginning of a different page. 
  Lower Case Tag And Attribute Names 
  Since XHTML is case sensitive, and since XHTML only accepts lower case HTML tags and attribute names, a general search and replace function was executed to replace all upper case tags with lowercase tags. The same was done for attribute names. We have always tried to use lower case names in our Web, so the replace function did not produce many real substitutions. 
  XHTML is case-sensitive, and only lowercase mark and attribute names, you can use the function to handle the replacement. 
  All Attributes Were Quoted 
  Since the W3C XHTML 1.0 Recommendation states that all attribute values must be quoted, every page in the web was checked to see that attributes values were properly quoted. This was a time-consuming job, and we will surely never again forget to put quotes around our attribute values. 
  Use brackets to attribute cause, there is no simple method, it is this amount of time spent on work, as long as do not forget to recall that after the brackets on the line. 

  Empty Tags: <hr>, <br> and <img> 
  Empty tags are not allowed in XHTML. The <hr> and <br> tags should be replaced with <hr /> and <br />. 

  This produced a problem with Netscape that misinterpreted the <br/> tags. We don't know why, but changing it to <br /> worked fine. After that discovery, a general search and replace function was executed to swap the tags. 

  A few other tags (like the <img> tag) were suffering from the same problem as above. We decided not to close the <img> tags with </ img>, but with /> at the end of the tag. This was done manually. 
  Had too wordy.    That is the mark just The Web Site Was Validated 
  After that, all pages were validated against the official W3C DTD with this link: XHTML Validator. A few more errors were found and edited manually. The most common error was missing </ li> tags in lists. 
  Your website can be official XHTML validity check to be verified with more errors will be detected and border manual, and the most common mistake is to forget the list, write </ li> has. 
  Should we have used a converting tool? Well, we could have used TIDY. 
  TIDY can use the conversion tools 
  Dave Raggett's HTML TIDY is a free utility for cleaning up HTML code. It also works great on the hard-to-read markup generated by specialized HTML editors and conversion tools, and it can help you identify where you need to pay further attention on making your pages more accessible to people with disabilities. 
  Dave Raggett's HTML TIDY HTML is used to optimize the code free software, it can also good to deal with those from special HTML editors and conversion tool for the curious markings at the same time, it can help you who you must logo from a long-term attention to the angle of your pages can be used by people with disabilities? 
  The reason why we didn't use Tidy? We knew about XHTML when we started writing this web site. We knew that we had to use lowercase tag names and that we had to quote our attributes. So when the time came (to do the conversion), we simply had to test our pages against the W3C XHTML validator and correct the few mistakes. AND - we have learned a lot about writing "tidy" HTML code. 
  We do not use TIDY reason is that when we do this site when we know XHTML, lowercase and the quotes we know.    So when the time we need to be converted simply by the W3C XHTML validator of the few to rectify our mistakes.    And, we have to know how to write a clean HTML code. 

  Why XHTML Modularization? 
  Why modular design XHTML? 
  XHTML is a simple but large language, containing most of the functionality a web developer will need. 
  XHTML Although simple, but many of its contents, including a network designer needs of the vast majority of functions. 
  For some purposes XHTML is too large and complex, and for other purposes it is much too simple. 
  On the one hand, many elements XHTML complex, but from another perspective it is very simple 
  By splitting XHTML into modules, the W3C (World Wide web Consortium) has created small and well-defined sets of XHTML elements that can be used separately for simple devices as well as combined with other XML standards into larger and more complex applications. 
  To XHTML divided into small modules, the W3C has already established a small definition of the good elements of a series of XHTML, they can be independent of XML and other standards into a large and more complex procedures for the use of simple equipment. 
  With modular XHTML, product and application designers can: 
  XHTML through the model, programmers can do the following things: 
  1.Choose the elements to be supported by a device using standard XHTML building blocks. 
  2.Add extensions to XHTML, using XML, without breaking the XHTML standard. 
  3.Simplify XHTML for devices like hand held computers, mobile phones, TV, and home appliances. 
  4.Extend XHTML for complex applications by adding new XML functionality (like MathML, SVG, Voice and Multimedia). 
  5.Define XHTML profiles like XHTML Basic (a subset of XHTML for mobile devices). 
  1.    Can be used to select those building blocks XHTML standard equipment supported by the elements. 
  2.    XHTML standards in complying with the concurrent use of XHTML XML can be extended. 
  3.    XHTML can be applied to a simplistic as handheld computers, and mobile phones, television and home appliance equipment. 
  4.    By joining heart XML capabilities (such as voice, multimedia) XHTML extended to the design of complex procedures. 
  5.    Like XHTML Basic (XHTML mobile devices for a subset of) as to define the contours of XHTML. 

  XHTML Modules 

  Module nameDescriptionApplet ModuleDefines the deprecated * applet element.Base ModuleDefines the base element.Basic Forms ModuleDefines the basic forms elements.Basic Tables ModuleDefines the basic table elements.Bi-directional Text ModuleDefines the bdo element.Client Image Map ModuleDefines browser side image map elements. Edit ModuleDefines the editing elements del and ins.Forms ModuleDefines all elements used in forms.Frames ModuleDefines the frameset elements.Hypertext ModuleDefines the a element.Iframe ModuleDefines the iframe element.Image ModuleDefines the img element.Intrinsic Events ModuleDefines event attributes like onblur and onchange . Legacy ModuleDefines deprecated * elements and attributes.Link ModuleDefines the link element.List ModuleDefines the list elements ol, li, ul, dd, dt, and dl.Metainformation ModuleDefines the meta element.Name Identification ModuleDefines the deprecated * name attribute.Object ModuleDefines the object and param elements.Presentation ModuleDefines presentation elements like b and i.Scripting ModuleDefines the script and noscript elements.Server Image Map ModuleDefines server side image map elements.Structure ModuleDefines the elements html, head, title and body.Style Attribute ModuleDefines the style attribute.Style Sheet ModuleDefines the style element.Tables ModuleDefines the elements used in tables.Target ModuleDefines the target attribute.Text ModuleDefines text container elements like p and h1. 

  * Deprecated elements should not be used in XHTML. 

  * Deprecated elements should not be used in XHTML.