I'm trying to make a transition effect with background-color when hovering menu items but it does not work. Here is my CSS code:

#content #nav a:hover {
color: black;
background-color: #AD310B;
    /* Firefox */
    -moz-transition: all 1s ease-in;
    /* WebKit */
    -webkit-transition: all 1s ease-in;
    /* Opera */
    -o-transition: all 1s ease-in;
    /* Standard */
    transition: all 1s ease-in;
}

The #nav div is a menu ul list of items.

Thank you for your help.