Differences Between XHTML And HTML
You can prepare yourself for XHTML by starting to write strict HTML.
How To Get Ready For XHTML
XHTML is not very different from
the HTML 4.01 standard.
So, bringing your code up to the 4.01 standard is a good start. Our
complete HTML 4.01 reference can help
you with that.
In addition, you should start NOW to write your HTML
code in lowercase letters, and NEVER skip ending tags
(like </p>).
Happy coding!
The Most Important Differences:
- XHTML elements must be properly nested
- XHTML elements must always be closed
- XHTML elements must be in lowercase
- XHTML documents must have one root element
XHTML Elements Must Be Properly Nested
In HTML, some elements can be improperly nested within each other, like this:
<b><i>This text is bold and italic</b></i>
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In XHTML, all elements must be properly nested within each other, like this:
<b><i>This text is bold and italic</i></b>
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Note: A common mistake with nested lists, is to forget that the
inside list must be within <li> and </li> tags.
This is wrong:
<ul>
<li>Coffee</li>
<li>Tea
<ul>
<li>Black tea</li>
<li>Green tea</li>
</ul>
<li>Milk</li>
</ul>
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This is correct:
<ul>
<li>Coffee</li>
<li>Tea
<ul>
<li>Black tea</li>
<li>Green tea</li>
</ul>
</li>
<li>Milk</li>
</ul>
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Notice that we have inserted a </li> tag after the </ul> tag
in the "correct" code example.
XHTML Elements Must Always Be Closed
Non-empty elements must have an end
tag.
This is wrong:
<p>This is a paragraph
<p>This is another paragraph
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This is correct:
<p>This is a paragraph</p>
<p>This is another paragraph</p>
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Empty Elements Must Also Be Closed
Empty elements must either have an end tag or the start tag must end with />.
This is wrong:
A break: <br>
A horizontal rule: <hr>
An image: <img src="happy.gif" alt="Happy face">
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This is correct:
A break: <br />
A horizontal rule: <hr />
An image: <img src="happy.gif" alt="Happy face" />
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XHTML Elements Must Be In Lower Case
The XHTML specification defines that the tag names and attributes need to be
lower case.
This is wrong:
<BODY>
<P>This is a paragraph</P>
</BODY>
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This is correct:
<body>
<p>This is a paragraph</p>
</body>
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XHTML Documents Must Have One Root Element
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:
<html>
<head> ... </head>
<body> ... </body>
</html>
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