bootstrap.css

.carousel-inner > .item {
    position: relative;
    display: none;
    -webkit-transition: 0.6s ease-in-out left;
    -moz-transition: 0.6s ease-in-out left;
    -o-transition: 0.6s ease-in-out left;
    transition: 0.6s ease-in-out left;
}