function einblenden(element)
{

   ausblenden();
   if (document.getElementById)
    document.getElementById(element).style.visibility = "visible";
	
}

function ausblenden()
{
 for(var i=2;i<=4;i++) 
 {
 	if (document.getElementById)
    document.getElementById("box"+i).style.visibility = "hidden";
 }
}