html,body {
    height:100%;
}
.h_iframe1 iframe {
    position:absolute;
    background: #030303;
    top:0px;
    left:0px;
    width:100%; 
    height:0px;
}
.h_iframe2 iframe {
    position:absolute;
    bottom:0;
    right:0;
    width:100%; 
    height:calc(100%);
}