.menu-left.menu-mobile-deroule-vertical #container-menu{
    position:fixed;
    padding-top:60px;
    height:100%;
    -webkit-transition-property: all;
    -webkit-transition-duration: 0.1s;
    -webkit-transition-timing-function: ease-out;
    /* When being supported by FF */
    -moz-transition-property: all;
    -moz-transition-duration: 0.1s;
    -moz-transition-timing-function: ease-out;
    /* … and if it's standardised one day (#optimism) */
    transition-property: all;
    transition-duration: 0.1s;
    transition-timing-function: ease-out;
}