.singlepost.container-fluid {
    position: relative;
    width: 100%;
    height: 100vh;
    padding: 0;
    margin: 0;
    top: 0;
}

iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: none;
    max-width: 100%;
    max-height: 100%;
}