[Flash CS4 AS2] Stage too small/please resize message - please help!

I apologize for being completely new to Flash - the solution to this question may be really obvious, but I’m missing it. I’m trying to create an effect similar to the one on http://www.ff0000.com/ when the browser window is too small - a message appears and asks the viewer to increase the window size.

I thought this would do it, but it doesn’t seem to be working:

var stageListener:Object=new Object();
stageListener.onResize=function(){
    toosmall();
};

Stage.align="TL";
Stage.scaleMode="noScale";
Stage.addListener(stageListener);

function toosmall() {
            if (stage.stageWidth < 600 || stage.stageHeight < 600) {
                stuff._alpha = 0;
                stuff2._alpha = 100;
            }

            else
            {
                stuff._alpha = 100;
                stuff2._alpha = 0;
            }
}
toosmall();

Any help would be greatly appreciated- this is driving me crazy! Thank you!