var object_opacity = 100;
var direction = "down";

function change_text(target,text) {
  document.getElementById(target).style.zoom = 1;
  var speed = Math.round(500 / 100);
  if(direction == "down")
    object_opacity -= speed;
  else
    object_opacity += speed;
  setTimeout('opac("'+object_opacity+'","'+target+'",\''+text+'\')',speed);
}

function opac(opacity,id,text) {
  var object = document.getElementById(id).style;
  object.opacity = (opacity / 100);
  object.MozOpacity = (opacity / 100);
  object.KhtmlOpacity = (opacity / 100);
  object.filter = "alpha(opacity=" + opacity + ")";
  
  if( opacity == 0 ){
    direction = "up";
    document.getElementById(id).innerHTML = text;
  }
  if(opacity == 100 && direction == "up"){
    object_opacity = 100;
    direction = "down";
  }
  else{
    change_text(id,text);
  }
  
}