function getClickTag():String{
    for (var key:String in root.loaderInfo.parameters)
        if(key.toLowerCase()=="clicktag")
            return root.loaderInfo.parameters[key];
    return "";
}
clicker_mc.addEventListener(MouseEvent.CLICK,function():void {
    navigateToURL(new URLRequest(getClickTag()),"_blank");
});

http://adspecs.yahoo.co.uk/ynetwork/300x250

used for yahoo! clicktags in as3

AS3 Yahoo! clicktag button listener

ActionScript 3