function GoNav(id) {
      document.getElementById('Sub1').style.visibility = 'hidden';
      document.getElementById('Sub2').style.visibility = 'hidden';
      document.getElementById('Sub3').style.visibility = 'hidden';
      document.getElementById('Sub4').style.visibility = 'hidden';
      document.getElementById('Sub5').style.visibility = 'hidden';
      document.getElementById('Sub'+id).style.visibility = 'visible';
    }

    function HideNav(id) {
      if(id==0){
        document.getElementById('Sub1').style.visibility = 'hidden';
        document.getElementById('Sub2').style.visibility = 'hidden';
        document.getElementById('Sub3').style.visibility = 'hidden';
        document.getElementById('Sub4').style.visibility = 'hidden';
        document.getElementById('Sub5').style.visibility = 'hidden';
      }
      else{
        document.getElementById('Sub'+id).style.visibility = 'hidden';
      }
    }

    window.onload=function(){
      document.getElementById('Sub1').style.visibility = 'hidden';
      document.getElementById('Sub2').style.visibility = 'hidden';
      document.getElementById('Sub3').style.visibility = 'hidden';
      document.getElementById('Sub4').style.visibility = 'hidden';
      document.getElementById('Sub5').style.visibility = 'hidden';
    }