If you have a xml file with this content:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"  
                xmlns:="http://support.procad.de"
                version="1.0">
</xsl:stylesheet>

It should probably catch that the attribute xmlns:="http://support.procad.de" is missing an alias/name. It should be either xmlns="http://support.procad.de" or something like xmlns:procad="http://support.procad.de"

Opening the same file in Chrome will render:
"This page contains the following errors:
error on line 3 at column 7: Failed to parse QName 'xmlns:'
Below is a rendering of the page up to the first error."

Firefox:
XML Parsing Error: not well-formed
Location: file:///C:/temp/test.xml
Line Number 3, Column 23:
                xmlns:="http://support.procad.de"
----------------------^