function navi2 (linkid)
{	
	leeren();
	 document.getElementById(linkid).style.display = 'block';
}

function leeren()
{
	document.getElementById('bilder').style.display = 'none';
  document.getElementById('sport').style.display = 'none';
}

var opened = "close";
function link_ext_open(linkextid)
{

clean_ext(linkextid);

  if(opened == "close")
  {
  document.getElementById(linkextid).style.display = 'block';
  opened = "open";
  }
  else
  {
  document.getElementById(linkextid).style.display = 'none';
  opened = "close";
  }
}

function clean_ext(linkextid)
{
  if(linkextid == "link_ext_1")
  {
    document.getElementById('link_ext_2').style.display = 'none';
  }
  else 
  {
   document.getElementById('link_ext_1').style.display = 'none';
  }  
}