function tr_visibl(val)
{
	var tr  = document.getElementById("v"+val);
	var td  = document.getElementById("t"+val); 

	if(tr.className == "tr_close")
	{
		tr.className = "tr_open";
		td.className = "head_o";
	}
	else
	{
		tr.className = "tr_close";
		td.className = "head_c";
	}
}