As defined in the XSLT specification, in section 2.5 :
An element enables forwards-compatible mode for itself, its attributes, its descendants and their attributes if either it is an xsl:stylesheet element whose version attribute is not equal to 1.0. (...)
(...)
If an element is processed in forwards-compatible mode, then:
- if it is a top-level element and XSLT 1.0 does not allow such elements as top-level elements, then the element must be ignored along with its content.
This document contains the following XSLT stylesheet appended:
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If your browser supports XSLT, and you are reading this document, then your browser ignored a unknown top-element from the xsl stylesheet therefore conforming to rule one of forward compatible processing. But the stylesheet has version 1.0 therefore forward compatible processing MUSTN'T be enabled, so instead of reading this you should see a XSLT processing failed message or error.