Menu problems

Hello two questions....(sorry for my little inglish)....

please...go to www.libertasnuotolugo.it and look the menu....

1) with the mouse move on "home" "chi siamo" "corsi e livelli" "gallery" "contatti" "amici" "download"

why the children page of "CORSI E LIVELLI" have white background? the children page of "CONTATTI" have whitout background and is good!!!

2) Now the children page of "CORSI E LIVELLI" and "CONTATTI" is left justified...it's possible center justified???

thanks