var subs_array = new Array("sub1","sub2","sub3","sub4","sub5","sub6","sub7","sub8","sub9","sub10","sub11","sub12","sub13","sub14","sub15","sub16");

function displaySubs(the_sub)
{
  	if (document.getElementById(the_sub).style.display != "none")
	{
	  	for (i=0; i<=subs_array.length; i++)
		{
	    	var my_sub = document.getElementById(subs_array[i]);
	    	my_sub.style.display = "none";
	 	}
    }
  	document.getElementById(the_sub).style.display = "block";
}