.css-serial {
  counter-reset: serial-number;  /* Set the serial number counter to 0 */
}

.css-serial td:first-child:before {
  counter-increment: serial-number;  /* Increment the serial number counter */
  content: counter(serial-number);  /* Display the counter */
}

table, th, td {
  
  border: 1px solid black;
  padding: 5px;
  background-color: #f1f1c1;
}