CSS Webkit过渡-淡入慢于淡入。

.box{
    background:#FFF;
    -webkit-transition: background 0.5s;
}

.box:hover{
    background:#000;
}

-wekbkit-transition-IN: background 1s;
-webkit-transition-OUT: background 10s;

.box{
    background: white;
    -webkit-transition: background 5s;
}
.box:hover{
    background: olive;
    -webkit-transition: background 1s;
}