Categories disappear after mouseover

Hi,
another issue I meet !

In the main layout, AUTHOR CATEGORIES are correctly displayed at first but each one disappears after mouse over on its text.
That doesn't happen with the QUOTES CATEGORIES
All what I encounter today is met using Joomla! 3.2.0

Edited for more info : Same thing for avatar : disappears after mouseover, same thing for the navigation arrows of the quotes

Better than a speach : http://www.testfg.org/index.php/le-club/actualite-des-athletes