Currently:

When you open a dictionary (or preferred dictionary with "F") it opens in the corner of the browser window. If you then open / refresh for another word it opens back at the corner of the browser window.

Suggestion:

If the dictionary window has been moved by the user and is still open. Keep it's position on screen and only refresh the contents.

When using multiple screens or tiling browser windows on a bigger screen, it is helpful if the dictionary doesn't obscure the content being read and remained where positioned by the user.