function validateForm(fm_id, fm_elem_array, style_error, style_ok) {
  var result = true;
  for (var i = 0; i<=fm_elem_array.length; i++) {  
    var fm = document.getElementById(fm_id);
    var fm_elem_id = fm_elem_array[i];
    var fm_elem = document.getElementById(fm_elem_id);
    if (fm_elem != null) {
      if (fm_elem.value == '') {
        fm_elem.className = style_error;
        result = false;
      } else {
        fm_elem.className = style_ok;
      }
    }    
  }
  if (!result) { 
    alert ('Bitte füllen Sie das Formular zuerst vollständig aus!'); 
  }
  return result;
}

function keyboardAction (event) {
  var keycode = event.keyCode;  
  var key = String.fromCharCode(keycode).toLowerCase();
  
  if ((key == 'p') || (keycode == 37)){
    elem = document.getElementById('goto_prev');
    if (elem != null) {       
      document.location.href = elem.href;
    }
  } else if ((key == 'n') || (keycode == 39)){ 
    elem = document.getElementById('goto_next');
    if (elem != null)
      document.location.href = elem.href;
  }
}

function initJS()
{
  document.onkeydown = keyboardAction;
}