function sipka(w){
  var num = 0;

  numArray = document.getElementByTagName('img');

  for(i=0;i<numArray.length;i++)
   if(!IsNaN(numArray[i].getAttribute('id')))
     num++;

  for(i=1;i<=num+1;i++) {
   if(!document.getElementById(i))
     continue;
   document.getElementById(i).src = './menu/arrow_gray.gif';
  }

  document.getElementById(w).src = './menu/arrow_blue.gif';
}