header {
  text-align: center;
  font-size: 25pt;
}
img { width: 250px; }
nav {
  text-align: center;
}
nav a {
  border: 1px solid blue;
  border-radius: 3px;
  padding: 1px 5px 1px 5px;
  margin: 2px;
  text-decoration: none;
  font-weight: bold;
  background-color: #9999ff;
  color: black;
}
main {
  margin-top: 5px;
}
td {
  vertical-align: top;
}
#images {
  margin-left: auto;
  margin-right: auto;
}