index.tpl.inc
line 67:
attribute was used more than once in the same tag:
title="{#unmark_linktitle#}" 4 occurencies!

lines 56 and 57:
The 2 characters "</" have been detected in a wrong place.
document.write("</a>" )
should read:
document.write("</a>" )

see http://www.htmlhelp.com/tools/validator/problems.html#script

ajax_preview.tpl
make all
</a> => </a>
and all
</div) => </div>
see above