Slide 3.6: Differences between XHTML and HTML
Slide 3.8: XHTML syntax
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Differences between XHTML & HTML (Cont.)

XHTML Elements Must Always Be Closed
Non-empty elements must have an end tag.

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

Empty Elements Must also Be Closed
Empty elements must have an end tag or the start tag must end with />.

Wrong Correct 
  A break: <!-- Can't show. -->
  A horizontal rule: <hr>
  An image: <img src="happy.gif"
    alt="Happy face">
 
  A break: <!-- Can't show. -->
  A horizontal rule: <hr />
  An image: <img src="happy.gif"
    alt="Happy face" />

XHTML Elements Must Be in Lower Case

Wrong Correct 
  <BODY>
    <P>This is a paragraph</P>
  </BODY>
 
  <body>
    <p>This is a paragraph</p>
  </body>

XHTML Documents Must Have One Root Element
All XHTML elements must be nested within the <html> root element. All other elements can have sub elements. Sub elements must be in pairs and nested within their parent element. The basic document structure is

Wrong Correct 
  <BODY>
    <P>This is a paragraph</P>
  </BODY>
 
  <html>
    <head> ... </head>
    <body> ... </body>
  </html>


Demonstration
The following demonstration shows how the script of HTML is displayed on the Web.