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XHTML is HTML written as XML.
What Is XHTML?
XHTML stands for EXtensible HyperText Markup Language
XHTML is almost identical to HTML
XHTML is stricter than HTML
XHTML is HTML defined as an XML application
XHTML is supported by all major browsers
Why XHTML?
Many pages on the internet contain “bad” HTML.
This HTML code works fine in most browsers (even if it does not follow the HTML rules):
This is bad HTML
Bad HTML
This is a paragraph
Today’s market consists of different browser technologies. Some browsers run on computers, and some browsers run on mobile phones or other small devices. Smaller devices often lack the resources or power to interpret “bad” markup.
XML is a markup language where documents must be marked up correctly (be “well-formed”).
If you want to study XML, please read our XML tutorial.
By combining the strengths of HTML and XML, XHTML was developed.
XHTML is HTML redesigned as XML.
The Most Important Differences from HTML:
Document Structure
XHTML DOCTYPE is mandatory
The xmlns attribute in is mandatory
, , , and are mandatory
XHTML Elements
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 Attributes
Attribute names must be in lower case
Attribute values must be quoted
Attribute minimization is forbidden
Is Mandatory
An XHTML document must have an XHTML DOCTYPE declaration.
A complete list of all the XHTML Doctypes is found in our HTML Tags Reference.
The , , , and elements must also be present, and the xmlns attribute in must specify the xml namespace for the document.
This example shows an XHTML document with a minimum of required tags:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
“http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd“>
<html xmlns="http://www.w3.org/1999/xhtml“>
Title of document
some content
XHTML Elements Must Be Properly Nested
In HTML, some elements can be improperly nested within each other, like this:
This text is bold and italic
In XHTML, all elements must be properly nested within each other, like this:
This text is bold and italic
XHTML Elements Must Always Be Closed
This is wrong:
This is a paragraph
This is another paragraph
This is correct:
This is a paragraph
This is another paragraph
Empty Elements Must Also Be Closed
This is wrong:
A break:
A horizontal rule:
An image: 
This is correct:
A break:
A horizontal rule:
An image:
XHTML Elements Must Be In Lower Case
This is wrong:
This is a paragraph
This is correct:
This is a paragraph
XHTML Attribute Names Must Be In Lower Case
This is wrong:
shahzade bau 