HTML Versus XHTML
HTML (HyperText Markup Language) and XHTML (eXtensible HyperText Markup Language) are both markup languages used to create web pages. While they share many similarities, there are key differences that distinguish them from each other. Understanding these differences is important for web developers.
1. Overview of HTML
HTML is the standard markup language for creating web pages. It is designed to be flexible and forgiving of errors, which makes it easier to write and work with.
Example:
A basic HTML document:
<!DOCTYPE html>
<html>
<head>
<title>HTML Example</title>
</head>
<body>
<h1>This is an HTML document</h1>
<p>HTML is flexible and forgiving.</p>
</body>
</html>2. Overview of XHTML
XHTML is a stricter and more XML-compliant version of HTML. It requires all elements to be properly closed, well-formed, and case-sensitive.
Example:
A basic XHTML document:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>XHTML Example</title>
</head>
<body>
<h1>This is an XHTML document</h1>
<p>XHTML is stricter and XML-compliant.</p>
</body>
</html>3. Key Differences Between HTML and XHTML
3.1 Document Structure
HTML allows a more flexible document structure, whereas XHTML requires a strict structure following XML rules.
3.2 Tag and Attribute Case Sensitivity
In HTML, tag and attribute names are case-insensitive. In XHTML, they must be lowercase.
Example:
HTML allows uppercase tags:
<DIV>This is a div element in HTML</DIV>XHTML requires lowercase tags:
<div>This is a div element in XHTML</div>3.3 Attribute Values
In HTML, attribute values can be unquoted or quoted with single or double quotes. In XHTML, attribute values must be quoted.
Example:
HTML with unquoted attribute values:
<input type=text value=Submit>XHTML with quoted attribute values:
<input type="text" value="Submit" />3.4 Closing Tags
HTML allows optional closing tags for some elements, while XHTML requires all tags to be closed properly.
Example:
HTML with optional closing tags:
<li>Item 1
<li>Item 2XHTML with mandatory closing tags:
<li>Item 1</li>
<li>Item 2</li>3.5 Self-Closing Tags
HTML allows self-closing tags without a slash. XHTML requires a slash in self-closing tags.
Example:
HTML self-closing tag:
<br>XHTML self-closing tag:
<br />4. Doctype Declarations
HTML and XHTML use different doctype declarations to define the document type and version.
Example:
HTML5 doctype:
<!DOCTYPE html>XHTML 1.0 Strict doctype:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">Conclusion
Both HTML and XHTML have their own use cases and advantages. HTML is more lenient and easier to write, making it suitable for most web development needs. XHTML, on the other hand, enforces stricter rules and is more suitable for applications that require XML compliance. Understanding the differences between HTML and XHTML helps web developers choose the right markup language for their projects.