What is XHTML Extensible hypertext markup language
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XHTML: Extensible HyperText Markup Language
XHTML (Extensible HyperText Markup Language) is a family of XML markup languages that mirrors or extends versions of the widely used HyperText Markup Language (HTML), the language in which web pages are formulated.
Core Concepts
- XML-based: XHTML is based on XML syntax, requiring strict adherence to XML rules, such as case sensitivity, proper nesting, and closing tags.
- HTML Compatibility: XHTML is designed to be compatible with HTML, allowing for gradual migration and coexistence of HTML and XHTML documents.
- Extensibility: XHTML inherits the extensibility of XML, allowing for the creation of custom elements and attributes.
- Stricter Syntax: XHTML imposes stricter syntax rules compared to HTML, enhancing validation and interoperability.
Advantages of XHTML
- Improved Structure: XHTML's XML-based structure provides a more well-defined and structured approach to web page creation.
- Better Validation: XHTML documents can be validated using standard XML tools, ensuring correctness and compatibility.
- Enhanced Interoperability: XHTML's strict syntax and XML compatibility improve interoperability with other XML-based technologies.
- Extensibility: The ability to create custom elements and attributes allows for tailored markup.
XHTML Versions
There are primarily three main versions of XHTML:
- XHTML 1.0: This version closely resembles HTML 4.01 but with stricter XML syntax. It exists in three flavors: Strict, Transitional, and Frameset.
- XHTML 1.1: A modular version of XHTML that focuses on removing deprecated elements and attributes from XHTML 1.0 Strict.
- XHTML 2: An ambitious attempt to redefine XHTML, but it didn't gain widespread adoption and was eventually withdrawn.
XHTML vs. HTML
While XHTML shares similarities with HTML, there are key differences:
| Feature | HTML | XHTML |
|---|---|---|
| Syntax | Relaxed, case-insensitive, optional closing tags | Strict XML syntax, case-sensitive, required closing tags |
| Validation | Lenient, browser-specific | Strict, XML-based validation |
| Extensibility | Limited | Enhanced through custom elements and attributes |
Decline of XHTML
Despite its advantages, XHTML has faced challenges in gaining widespread adoption compared to HTML:
- Browser Compatibility: While most modern browsers support XHTML, older browsers might have issues.
- Complexity: Stricter syntax can be more challenging for developers compared to HTML.
- HTML5 Emergence: The introduction of HTML5, which combines HTML, CSS, and JavaScript, has provided a more flexible and powerful web development platform.
Conclusion
While XHTML offered a more structured and extensible approach to web development, it didn't achieve the same level of adoption as HTML. However, the principles behind XHTML continue to influence web standards and development practices.