/* CSS Document */
header h1(color:red;)
body {
background-color: rgb(204, 255, 255);
margin: 0px 5px;
display: grid;
grid-template-colums: auto 350px;
}

body {
  background-color: lightblue;
}
   header { 
   color:white;
   background-color:green;
   text-align: center;
   font-family: sans-serif;
   grid-columns; 1 / 3;
   grid-row? 1 / 2;
   }
   
   
header h1, header h2{
margin: 0px;
padding: 5px 15px;
}
   nav {
  grid-column: 1 / 2;
grid-row: 2 / 3;

}

 nav a{
 background-color: black;
  padding: 5px  10px;
border: 4px outset grey;
margin: 2px; 
 color: white;
 text-decoration: none;
 font-family:sans-serif;
 display: block;
 line-height: 2;
 }

nav a:hover {
color:yellow;
background-color:green;
  }
   section {
   margin: 5px;
   grid-column: 1 / 2;
   grid-row: 2 / 3;
          }
  <ul>{
  list-style-type: square;
  } 
  table, tr, th, td {
  border: 1px solid black;
  border-collapse: collapse;
font-family: sans-serif;
  }

  th, td {
  height: 35px;
  width: 7%;
  text-align: center;
  }
    {
  th,tr:nth-child(even)
  background-color:#D2E3E9;
  }
  footer {
  color: white;
background-color:black;
text-align: left;
font-family: sans-serif;
font-size? x-small;
padding: 3px 15px;
grid-column: 1 / 3;
grid-row: 2 / 3;
    }