* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}


.navigation {
    width: 200px;
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    padding: 10px;
    border-right: 1px solid #e9e9e9;
}

.navigation li {
    margin: 10px 0;
}

.demo-frame {
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    left: 200px;
}

iframe[name='demo'] {
    display: block;
    width: 100%;
    height: 100%;
    border: none;
}