CSS3 grid-template-areas

<!doctype html>
<title>Example</title>
<style>
body { 
  display: grid;
  grid-template-areas: 
    "header header header"
    "nav article ads"
    "footer footer footer";
  grid-template-rows: 100px 1fr 70px;  
  grid-auto-columns: 20% 1fr 15%;
  grid-gap: 10px;
  height: 100vh;
  margin: 0;
  animation: myAnimation 1s ease 1s 5 alternate forwards;
  }
header, footer, article, nav, div {
  padding: 20px;
  background: gold;
}
#pageHeader {
  grid-area: header;
}
#pageFooter {
  grid-area: footer;
}
#mainArticle { 
  grid-area: article;      
  }
#mainNav { 
  grid-area: nav; 
  }
#siteAds { 
  grid-area: ads; 
  }

@keyframes myAnimation {
  100% {
  grid-template-areas: 
    "header article ads"
    "nav article ads"
    "footer footer ads";
  }
}  
</style>
<body>
  <header id="pageHeader">Header</header>
  <article id="mainArticle">Article</article>
  <nav id="mainNav">Nav</nav>
  <div id="siteAds">Ads</div>
  <footer id="pageFooter">Footer</footer>
</body>