th {
  padding: 10px;
  border-bottom: 1px solid black;
  font-weight: bold;
}
td {
  padding: 0 10px 0 10px;
  border-bottom: 1px solid black;
}
td.avail {
  background-color: #ccc;
}
td.avail a {
  display: block;
  text-decoration: none;
}