// accepts a pointer to the table cell in question,
 // and a boolean for whether to turn it on or off
 function lightup(cell,active) {
  on = "#000000";
  off = "#8D0000";

  if(active) {
   cell.style.backgroundColor=on;
   cell.style.cursor='hand';
  }
  else
   cell.style.backgroundColor=off;
 }