var nkactive = new Array();

function open_nk ( tid, id ){

  if ( nkactive[id] != id ){

    document.getElementById(tid).style.visibility='visible';
    document.getElementById(tid).style.position='relative';

    document.getElementById("boxnachkomme"+id).className = 'whitebox3';
    nkactive[id] = id;
  }else{
    document.getElementById(tid).style.visibility='hidden';
    document.getElementById(tid).style.position='absolute';  

    document.getElementById("boxnachkomme"+id).className = 'whitebox2';
    
    nkactive[id] = 0;    
  }
}