overlay Background CSS

.custom-header-media:before {
    background: -moz-linear-gradient(to top, rgba(0, 0, 0, 0) 0%, rgba(0, 0, 0, 0.3) 75%, rgba(0, 0, 0, 0.3) 100%);
    background: -webkit-linear-gradient(to top, rgba(0, 0, 0, 0) 0%, rgba(0, 0, 0, 0.3) 75%, rgba(0, 0, 0, 0.3) 100%);
    background: linear-gradient(to bottom, rgba(0, 0, 0, 0) 0%, rgba(0, 0, 0, 0.3) 75%, rgba(0, 0, 0, 0.3) 100%);
    filter: progid:DXImageTransform.Microsoft.gradient(startColorstr="#00000000", endColorstr="#4d000000", GradientType=0);
    bottom: 0;
    content: "";
    display: block;
    height: 100%;
    left: 0;
    position: absolute;
    right: 0;
    z-index: 2;
}