Self-Closing Span Tags: A Tale of XHTML and HTML
The question of whether HTML spans can be closed using depends on the underlying document type definition (DOCTYPE). This distinction lies between XHTML and HTML.
XHTML: Validating Self-Closing Tags
When using XHTML, all major browsers support self-closing tags like . In XHTML, which adheres to XML syntax, any custom element not defined as an empty element in the DTD must be closed explicitly. Therefore, self-closing tags are valid.
Consider the following example, which is valid because it specifies the document type as XHTML:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title></title>
</head>
<body>
<h2>Will test page</h2>
<p>some stuff <span class="drop" /></p>
</body>
</html>HTML: Invalidating Self-Closing Tags
However, in HTML, self-closing tags like are not valid. HTML follows a different syntax where certain elements are defined as empty elements. Spans are not included in this list.
If you switch the DOCTYPE to HTML, the example above becomes invalid:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title></title>
</head>
<body>
<h2>Will test page</h2>
<p>some stuff <span class="drop" /></p>
</body>
</html>Important Note:
While browsers will interpret all self-closing tags correctly if the MIME type is text/xml or application/xhtml xml, for pages served as text/html (the vast majority), only a specific set of tags can be self-closed.
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