function show(object) {
  document.getElementById(object).style.display = 'block';
}

function hide(object) {
  document.getElementById(object).style.display = 'none';
}

var prev_tip = null;
function showtip(id){
  if(prev_tip != null)
    toggleVisId(prev_tip);
  if(prev_tip != id){
    toggleVisId(id);
    prev_tip = id;
  }
  else{
    prev_tip = null;
  }
}


function selectonderwerp(select, first){
  $('gedaan_'+select.options[select.selectedIndex].value+'_div').style.display = 'block';
  if(first){
    $('first_select_div').style.display = 'none';
    $('after_select_div').style.display = 'block';
  }
}