il blocco core.NavigationLinks non esiste.

This is my problem! dear friends, am not an expert! so please be kind and simple...
when i sow a theme called gecko i donwloaded it and installed...and i like it very much and i would like to keep it. Now on the side menu i have this warning " WARNING: il(the) blocco core.NavigationLinks non esiste(doesn't exist)." what can i do? this is the url to my gallery http://www.pareus.netsons.org/gallery/main.php
am just waiting for ur resp... thank u..

I consulted another post in the forum similar to this one... but i didn't understand anything!!!!