Hi Greg,
I am not sure how you could have a normal sized email window, but an excessively large homepage window. Most people navigate from one to the other in one browser window, which would not allow for such a size change (as far as I know).
I highly recommend visiting the help page for whatever browser you are using, to see if they have any insight into why that may be happening as this would not be caused by visiting our webpage, unless a browser specific setting has been changed.
I hope that helps!