stayle.css

body {
  font-size: 17px;
  font-family: Arial, Helvetica, sans-serif;
  background: f4f4f4;
  line-height: 1.5 em;
  border-left: 3px solid #000;
  border-right: 3px solid #000;
}
header {
  background: #333;
  color: #fff;
  padding: 20px;
  text-align: center;
  border-top: 3px solid #000;
  border-bottom: 3px solid #000;
  margin-bottom: 10px;
  
  display: flex;
  justify-content: space-between;
  align-items: center;
}
#container {
  width: 90%;
  margin: auto;
  padding: 10px;
  text-align: center;
}
.butns {
  margin-top: 30px;
  border: 2px solid #000;
  padding: 10px 20px;
  font-size: 20px;
}

footer {
  background: #333;
  color: #fff;
  padding: 20px;
  text-align: center;
  border-top: 3px solid #000;
  border-bottom: 3px solid #000;
  margin-bottom: 10px;
}

a {
  color: #71a9fc;
}