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";
}