image flies up when wanting to see its bottom edge

[jidanni@xxxxxxxxxxx]

With http://tour.tpc.gov.tw/Transit/Bus/GetBus.asp?QBusID=100
do T (w3m-toggle-inline-images). Now try to see what the name of the
bus stop at the very bottom of the image is.

Well, it turns out it has no name. But the problem is as one tries to
put the bottom edge of the image into the center of the screen to make
sure, the whole image files up off the screen.
(I use http://jidanni.org/comp/configuration/.emacs-w3m )