function secBoard(n)
  {
    for(i=0;i<secTable.cells.length;i++)
      secTable.cells[i].className="sec1";
      secTable.cells[n].className="sec2";
    for(i=0;i<mainTable.tBodies.length;i++)
      mainTable.tBodies[i].style.display="none";
      mainTable.tBodies[n].style.display="block";
   }