as3 loader

programming flash
1

hello,
i just setup this loader i found on the net:

var l:Loader = new Loader();
l.contentLoaderInfo.addEventListener(ProgressEvent.PROGRESS, loop);
l.contentLoaderInfo.addEventListener(Event.COMPLETE, done);
l.load(new URLRequest("world.jpg"));

function loop(e:ProgressEvent):void{
    var perc:Number = e.bytesLoaded / e.bytesTotal;
    percent.text = Math.ceil(perc*100).toString();
}

function done(e:Event):void{
    removeChildAt(0);
    percent = null;
    addChild(l);
}

what i dont understand is that everytime i click the refresh page the loader shows up again(this time loading the image faster) but if the image is already in cache the loader should not show at all (?), i would like to achieve a loader that loads the image and after dont come up again everytime.