html, body {
    width: 100%;
    height: 100%;
    margin: auto;
    overflow: hidden;
}

iframe {
    position:fixed;
    top:0;
    left:0;
    bottom:0;
    right:0; 
    width:100%;
    height:100%; 
    border:none; 
    margin:0; 
    padding:0; 
    overflow:hidden; 
    z-index:999999;
}