body {
    background-color: #F5F5F5;
    color: #555;
    font-size: 1.1em;
    font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
}

.container {
    margin: 50px auto;
    max-width: 700px;
}

.element {
    max-width: 500px;
    height: 250px;
    border: 1px solid black;
    margin: 0 auto;
    background-image: linear-gradient(to right, white 50%, black 50%);
    /* equivalent to (to right, white, white 50%, black 50%, black) */

    background-size: 50px 100%;
    background-repeat: repeat;
}