Buttons Under Mouse Effect

Hey i try add to my buttons ( Home,FAQ,Search etc...) effect same as in my forum logo : http://seiya.forumotion.com/

I try :

Code:

#index:hover {
    opacity: 0.5;
}

I try this one but not working ;<
Later i try this one

Code:

.Index img {
  opacity: 0.9;}

Not working too 0 effects, any idea xd?

#Sloved.