function addEvent(obj, evType, fn){ 
 if (obj.addEventListener){ 
   obj.addEventListener(evType, fn, false); 
   return true; 
 } else if (obj.attachEvent){ 
   var r = obj.attachEvent("on"+evType, fn); 
   return r; 
 } else { 
   return false; 
 } 
}

function fill_and_hide_captcha() {
  value = document.getElementById('captcha_kontrola').getAttribute('value');
  document.getElementById('captcha_odpoved').setAttribute('value', value);
  value2 = document.getElementById('captcha_odpoved').getAttribute('value');
  if (value == value2 && value > 0 && value < 10)
    document.getElementById('captcha').style.display = 'none';
}

addEvent(window, 'load', fill_and_hide_captcha);