Introduction to HTML and XHTML

HTML (Hypertext Markup Language) and XHTML (Extensible Hypertext Markup Language) are both markup languages used to create and structure content on the web. While HTML is the traditional standard, XHTML represents a more stringent and XML-based approach to HTML.

Key Differences

Here are some key differences between HTML and XHTML:

Feature	HTML	XHTML
Syntax	Allows for loose syntax; some errors may be tolerated.	Strict syntax; all elements must be properly closed and nested.
Tag Case	Tags are case-insensitive.	Tags are case-sensitive; all tags must be in lowercase.
Attribute Case	Attributes are case-insensitive.	Attributes are case-sensitive; all attributes must be in lowercase.
Document Structure	Document structure is more lenient; optional closing tags are allowed.	Document structure must be strictly followed; all tags must be properly closed.
Document Type Declaration	HTML documents use a simpler DOCTYPE declaration.	XHTML documents require a more complex DOCTYPE declaration.

Examples

Here are examples of HTML and XHTML syntax:

<!-- HTML Example -->
<html>
    <head>
        <title>HTML Example</title>
    </head>
    <body>
        <h1>Welcome</h1>
        <p>This is an HTML example.</p>
    </body>
</html>

Welcome

This is an HTML example.

<!-- XHTML Example -->
<?xml version="1.0" encoding="UTF-8"?>
<!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>Welcome</h1>
        <p>This is an XHTML example.</p>
    </body>
</html>

Welcome

This is an XHTML example.

Choosing Between HTML and XHTML

While XHTML enforces a stricter syntax and is more suitable for documents that need to be compatible with XML-based systems, HTML is more flexible and is still widely used for general web development. The choice between HTML and XHTML depends on the requirements of the project and the need for strict compliance.