CSS

div background color change animation

transition: background-color 1000ms linear;

css animate background color change

#content #nav a {
    background-color: #FF0;
    
    -webkit-transition: background-color 1000ms linear;
    -moz-transition: background-color 1000ms linear;
    -o-transition: background-color 1000ms linear;
    -ms-transition: background-color 1000ms linear;
    transition: background-color 1000ms linear;
}

#content #nav a:hover {
    background-color: #AD310B;
}