function showhide_pref(which)
{
	off = which + '_off';
	on  = which + '_on';

	if (document.getElementById(off).style.display == "block")
	{
		document.getElementById(off).style.display = "none";
		document.getElementById(on).style.display = "block";				
	}
	else
	{
		document.getElementById(off).style.display = "block";
		document.getElementById(on).style.display = "none";
	}
}

var chunk	= new Array(1);
chunk[0]  = "cnaa";
chunk[1]  = "cpn";
chunk[2]  = "cwaea";
chunk[3]  = "dl1";
chunk[4]  = "dl2";
chunk[5]  = "dl3";
chunk[6]  = "dl4";
chunk[7]  = "instr";

var state = 'closed';

function showhide_chunk()
{
	for (i = 0 ; i < chunk.length; i++ )
	{								
		off = chunk[i] + '_off';
		on  = chunk[i] + '_on';

		if (state == 'closed' && document.getElementById(off).style.display)
		{
			document.getElementById(off).style.display = "block";
			document.getElementById(on).style.display = "none";	
		}
		else
		{
			document.getElementById(off).style.display = "none";
			document.getElementById(on).style.display = "block";
		}
	}

	if (state == 'closed')
	state = 'open';
	else
	state = 'closed';
}