HTML 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):
<html>
<head>
<title>This is bad HTML</title>
<body>
<h1>Bad HTML
<p>This is a paragraph
</body>
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.
XHTML was developed by combining the strengths of HTML and XML.
XHTML is HTML redesigned as XML.
The Most Important Differences from HTML:
Document Structure
- XHTML DOCTYPE is mandatory
- The xmlns attribute in <html> is mandatory
- <html>, <head>, <title>, and <body> 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
