see http://zkfiddle.org/sample/2u3aium/1-Problems-with-listheader-in-IE11-and-ZK-6-5-3
the list headers have centered alignment where other browsers have left-alignment

workaround is to add a "th

" to make IE11 inherit the style
see upgraded fiddle
http://zkfiddle.org/sample/2u3aium/2-Problems-with-listheader-in-IE11-and-ZK-6-5-3

The issue does not occur in ZK7, since according css classes have been inserted already in that version