Processor Version Stylesheet
The XSLT stylesheet at http://www.mulberrytech.com/xsl/xsl-list/processor-version.xsl identifies vendor information for any conformant XSLT processor that runs it.
Test your browser for XSLT support by linking directly to this file, or save it locally and check any XSLT engine by transforming any document with it. (Running the stylesheet on itself will work. The result is HTML.)