function GoNav(cid){
				 document.getElementById("sub_nav_1").style.display="none";
				 document.getElementById("sub_nav_2").style.display="none";
				 document.getElementById("sub_nav_3").style.display="none";
				 document.getElementById("sub_nav_4").style.display="none";
				 document.getElementById("sub_nav_5").style.display="none";
				 document.getElementById("sub_nav_6").style.display="none";
				 document.getElementById(cid).style.display="block";
}