I really advise you do not do it. Not because it is 'cheating', which I do not care if you do or do not -- but because it seriously breaks and bugs the game, making it unplayable. It really duplicates things... and duplicates them some.. and some more.. and some more.. until the end of time, causing your computer to run out of storage, memory, etc. Okay, that is a small exaggeration; You can always close the page / browser to stop it, but then you cannot play the game. So why do it?
Also, my post / comment (above) already said how to do it.