XSLint is an XSL lint checker. It reads an XSL stylesheet and looks
for semantic errors.

XSLint looks for:
* an incorrect XSLT URI;
* failure to provide a version;
* duplicate match patterns;
* modes that are used but never defined;
* modes that are defined but never used;
* named templates that are used but never defined;
* named templates that are defined but never used;
* templates that use name= where match= was probably intended;
* xsl:call-template elements that contain anything other than xsl:with-param;
* variable/parameter references that are not defined at the point of use;
* fo: elements that aren't part of the XSL 1.0 PR;
* fo: element properties that aren't part of the XSL 1.0 PR.

WWW: http://nwalsh.com/xml/xslint/