<div class="item"></div>

/* Slides an element to the right */
.item {
    background: black;
    height: 50px;
    width: 50px;
    animation-name: slide;
    animation-duration: 4s;
    animation-iteration-count: infinite;  
    animation-timing-function: ease;
}

@keyframes slide {
    from {
        transform: translateX(0px);
    }
    to {
        transform: translateX(100px);
    }
}