html,
body {
    height: 100%;
    width: 100%;
    background: #303f9f;
    background: -webkit-linear-gradient(0deg, #1976d2, #42c7db) !important;
    background: -moz- oldlinear-gradient(0deg, #1976d2, #42c7db) !important;
    background: -o-linear-gradient(0deg, #1976d2, #42c7db) !important;
    background: linear-gradient(0deg, #1976d2, #42c7db) !important;
}
html {
    display: table;
    margin: auto;
}
body {
    display: table-cell;
    vertical-align: middle;
}