.bounce {
    -moz-animation: bounce 3s infinite;
    -webkit-animation: bounce 3s infinite;
    animation: bounce 3s infinite;
}

@-moz-keyframes bounce {
    0%, 20%, 50%, 80%, 100% {
        -moz-transform: translateY(0);
        transform: translateY(0);
    }

    40% {
        -moz-transform: translateY(-30px);
        transform: translateY(-30px);
    }

    60% {
        -moz-transform: translateY(-15px);
        transform: translateY(-15px);
    }
}

@-webkit-keyframes bounce {
    0%, 20%, 50%, 80%, 100% {
        -webkit-transform: translateY(0);
        transform: translateY(0);
    }

    40% {
        -webkit-transform: translateY(-30px);
        transform: translateY(-30px);
    }

    60% {
        -webkit-transform: translateY(-15px);
        transform: translateY(-15px);
    }
}

@keyframes bounce {
    0%, 20%, 50%, 80%, 100% {
        -moz-transform: translateY(0);
        -ms-transform: translateY(0);
        -webkit-transform: translateY(0);
        transform: translateY(0);
    }

    40% {
        -moz-transform: translateY(-30px);
        -ms-transform: translateY(-30px);
        -webkit-transform: translateY(-30px);
        transform: translateY(-30px);
    }

    60% {
        -moz-transform: translateY(-15px);
        -ms-transform: translateY(-15px);
        -webkit-transform: translateY(-15px);
        transform: translateY(-15px);
    }
}

.preloader img {
    margin: auto auto;
    position: fixed;
    top: 50%;
    left: 50%;
    width: 15em;
    height: 9em;
    margin-top: -4em; /*set to a negative number 1/2 of your height*/
    margin-left: -7em; /*set to a negative number 1/2 of your width*/
}