Some games retain their data not in normal web browser cookies but in Flash cookies. If you've tried to clear your browser cache but find that the game website still seems to know things about your game (such as how much progress you've made as a guest), the following instructions may help:
- Access the Website Storage Settings panel on the Flash Player Help webpage: http://www.macromedia.com/support/documentation/en/flashplayer/help/settings_manager07.html
- Click the tab for Website Storage Settings.
- Click "Delete all sites".
- Reload the website for your game. It should now have forgotten all progress and treat you as a brand new player.