body, html {
    height: 100%;
    margin: 0;
    padding: 0;
}

body {
    display: grid;
    grid-template-columns: 150px auto;
    grid-template-rows: 95px auto 20px;
    grid-template-areas: 
      "header header"
      "sidebar main"
      "footer footer";
  }

iframe {
    margin: 0;
    padding: 0;
    border: none;
}

iframe[name=boven] {
    grid-area: header;
    width: 100%;
    height: 100%;
}

iframe[name=inhoud] {
    grid-area: sidebar;
    width: 100%;
    height: 100%;
}

iframe[name=hoofd] {
    grid-area: main;
    width: 100%;
    height: 100%;
}

iframe[name=onder] {
    grid-area: footer;
    width: 100%;
    height: 100%;
}