The string `http://www.w3.org/1999/xhtml` is not code but rather a namespace...

August 26, 2025 at 11:26 AM

The string http://www.w3.org/1999/xhtml is not code but rather a namespace URI (Uniform Resource Identifier) used in XML and XHTML documents. It typically appears in XML or HTML code to associate elements with the XHTML standard.

For example, it is often used like this in XHTML documents:

<html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <title>Example</title>
    </head>
    <body>
        <p>Hello, World!</p>
    </body>
</html>

Here’s what it does:

The xmlns="http://www.w3.org/1999/xhtml" attribute defines the default XML namespace for all elements in the document.
The URI specifically points to the XHTML 1.0 namespace, which signifies that the document adheres to the XHTML specification standardized by the World Wide Web Consortium (W3C).

It ensures that tools like browsers and XML parsers can correctly interpret and validate the document as XHTML.

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