navbar.css

.navbar-collapse {
    overflow-x: visible;
    padding-right: 15px;
    padding-left: 15px;
    border-top: 1px solid transparent;
    box-shadow: inset 0 1px 0 rgba(255,255,255,0.1);
    -webkit-overflow-scrolling: touch;
}

.collapse {
    display: none;
    visibility: hidden;
}


.navbar-collapse.in {
    overflow-y: auto;
}
.collapse.in {
    display: block;
    visibility: visible;
}