Try to analyse your Atahualpa site with this black hat SEO detector: http://tool.motoricerca.info/spam-detector/
Probably you will get the same error messages:
Invisible text found. Method(s): CSS 'display' property set to 'none'.
Invisibility purpose: Impossible to say.
I think it is caused by the Print Style definition in the css.php. (e.g.: *lang(en) td#left {display: none; }
I do not know if it is a real problem. Do the searching bots detect it as a black hat SEO activity? Maybe…
What do you think?