body, html {
    margin: 0;
    padding: 0;
    height: 100%;
    width: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
}

#main {
    display: flex;
    width: 100%;
    height: 100%;
}

#iframecontainer1, #iframecontainer2 {
    flex: 1;
    height: 100%;
}

iframe {
    width: 100%;
    height: 100%;
    border: none;
}