If you think about it slightly differently.. what's wrong with just hitting the back space key? That's actually less effort than having to hit two separate keys and achieves the same result. While it is minuscule and can likely be cached by browser software, it's better to have as little code as possible on a website in order to minimize the bandwidth usage across all the views per day. It also has the potential to introduce a new attack vector - however small the possibility may be, so better to leave it for truly essential requirements and reduce the surface area for bugs to hide in.