GradientAnimator

.css-selector {
    background: linear-gradient(90deg, #000080, #1084d0);
    background-size: 400% 400%;
    -webkit-animation: Windows98LoadingBar 2s ease infinite;
    -moz-animation: Windows98LoadingBar 2s ease infinite;
    -o-animation: Windows98LoadingBar 2s ease infinite;
    animation: Windows98LoadingBar 2s ease infinite;
}
@-webkit-keyframes Windows98LoadingBar {
    0%{background-position:0% 50%}