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";
}