html, body {
    height: 100%;
}

iframe {
    width: 100%;
}

@media screen and (min-width: 550px) {
    #navframe {
        border: none;
        height: 8%;
    }

    #mainframe {
        height: 85%;
    }

    #mainframe body {
        max-width: 600px;
        margin: auto;
    }
}

@media screen and (max-width: 550px) {
    #navframe {
        border: none;
        height: 14%;
    }
    #mainframe {
        height: 80%;
    }
}