/**
 * Scrolling button
 * by Stanislav Nevolin, stanislav@nevolin.info
 */
var scrollToTopic = function(idTopic) {
  docScroller = new Fx.Scroll(document.getDocument());
  docScroller.setOptions({
    duration:500,
    offset: {
          'x': 0,
          'y': 0
      }
  });
  var topic = $('topic_' + idTopic);
  var deltaY = topic.getDimensions().height/2-window.getSize().y/2;
  if (deltaY > 0) {
    deltaY = 0;
  }
  docScroller.start(0, topic.getPosition().y + deltaY);
  return false;
}