html,
body {
    width: 100%;
    height: 100%;
    background: #3797bd;
    background: linear-gradient(6deg, rgba(55, 151, 189, 1) 0%, rgba(87, 199, 133, 1) 50%, rgba(237, 221, 83, 1) 100%);
    text-align: center;

}

.absoluteCenter {
    /* Must manually set width/height */
    width: 800px;
    height: 300px;

    /* The magic centering code */
    margin: auto;
    position: absolute;
    top: 0;
    bottom: 0;
    /* Aligns Vertically - Remove for Horizontal Only */
    left: 0;
    right: 0;
    /* Aligns Horizontally - Remove for Vertical Only  */

    /* Prevent div from overflowing main window */
    max-width: 100%;
    max-height: 100%;
    overflow: auto;
}

/* IE 7 and Below */
:first-child+html .absoluteCenter,
* html .absoluteCenter {
    /* Place code here to override all above values, and add IE friendly centering */
}