function visibleandhidenavname(indexzahl)
 {   
    var navigation = new Array();
	navigation[0]="navigationinternetliteratur";
	navigation[1]="navigationpapier";
	navigation[2]="navigationlinks";
	navigation[3]="navigationueberblick";
	navigation[4]="navigationbio";
	navigation[5]="navigationgalerie";
	//alert(name);
	
	for (n=0; n < 6; n++)
	{
	 navname = navigation[n];
	 //alert(navname);
	 document.getElementById(navname).style.visibility = "hidden";
	}
	
	navname=navigation[indexzahl]
	//alert(navname);
	document.getElementById(navname).style.visibility = "visible";
	return false;
   
  }