function setOpacity(obj, opacity) {
  opacity = (opacity == 100) ? 99.999 : opacity;

  // IE/Win
  obj.style.filter = "alpha(opacity:"+opacity+")";

  // Safari<1.2, Konqueror
  obj.style.KHTMLOpacity = opacity/100;

  // Older Mozilla and Firefox
  obj.style.MozOpacity = opacity/100;

  // Safari 1.2, newer Firefox and Mozilla, CSS3
  obj.style.opacity = opacity/100;
}

function _fade(objId, opacity, opacityStep, delay) {
  if (document.getElementById) {
    obj = document.getElementById(objId);
    if (opacity < 0){
      setOpacity(obj, 0);
    }else if(opacity > 100) {
      setOpacity(obj, 100);
    }else{
      opacity += opacityStep;
      setOpacity(obj, opacity);
      window.setTimeout("_fade('"+objId+"',"+opacity+","+opacityStep+","+delay+")", delay);
    }
  }
}

/* public */

function fadeIn(objId, opacityStep, delay) {
  imageId = objId;
  image = document.getElementById(imageId);
  image.style.visibility = 'visible';
  _fade(imageId, 0, opacityStep, delay);
}

function fadeOut(objId, opacityStep, delay) {
  imageId = objId;
  image = document.getElementById(imageId);
  //setOpacity(image, 0);
  if(opacityStep == -100){
    setOpacity(image, 0);
    image.style.visibility = 'hidden';
  }else{
      _fade(imageId, 100, opacityStep, delay);
  }
  //image.style.visibility = 'hidden';
}