html, body {
    margin: 0;
    padding: 0;
}

.main {
    max-width: 800px;
    height: 100%;
    margin: 0 auto;
    padding: 20px;
}

.nav {
    border: 3px solid red;
    padding: 12px 12px 120px;
    float: right;
    width: 200px;
}

.content {
    border: 3px solid blue;
    padding: 12px 12px 120px;
    margin-right: 230px;
}


@media screen and (max-width: 960px) {
}

@media screen and (max-width:480px) {
    .main, .nav, .content {
        width: auto;
        height: auto;
        float: none;
        margin: 0;
    }
    .main {
        padding: 0;
    }
}