header h1 {
color: black;
background: green;
font-family Ariel, sans-serif;
text-align: center;
margin: 0 auto;
}
table, th, td {
border: 1px solid black;
}
table {
 border-collapse: collapse;
 }
 th { 
 background-color: #D9D9D9;
 }
tr:nth-child(odd) {
background-color: #C3C3C3 ;
}
td {
width: 6%;
text-align: center;
}