function showsub_b(id)
{
for (i = 0;i<2;i++)
{
document.getElementById("tab_b"+i).className = "yk_menu_bj_02";
document.getElementById("sub_b"+i).style.display = "none";
      }
document.getElementById("tab_b"+id).className = "yk_menu_bj_01";
document.getElementById("sub_b"+id).style.display = "";
   }

  function showsub_a(id)
	{
		for (i = 0;i<3;i++)
		{
			document.getElementById("tab_a"+i).className = "yk_menu_bj_02";
			document.getElementById("sub_a"+i).style.display = "none";
		}
			document.getElementById("tab_a"+id).className = "yk_menu_bj_01";
			document.getElementById("sub_a"+id).style.display = "";
	}



var a = document.getElementById("main");
   a.style.left=(document.body.clientWidth/2-a.clientWidth/2)+"px";
   a.style.top=(document.body.scrollTop+document.body.clientHeight/2-a.clientHeight/2)+"px";