2.1.1 [W3C-XSLT] Section 1, Introduction
The specification states:
The MIME media types text/xml and application/xml should be used for XSLT stylesheets. It is possible that a media type will be registered specifically for XSLT stylesheets; if and when it is, that media type may also be used.
An XML style sheet is transformed only when type="
text/xsl". XML style sheets of type="
text/xml" or of type="
application/xml" are not transformed.
Processing instructions for XML style sheets are supported, but an XML style sheet is not automatically associated with XML content.