FF jumps about when enlarging window

[firefox 3.5.3]
I often enlarge individual articles of online news papers. FF pops up the
article in a separate window all right, but that window always jumps to the
same, off centre, position. I have tried dragging the window to the middle,
closing down FF and trying again, but no matter what I do, the pop up window
will shoot to the bottom right hand area of my screen just after is had fully
loaded.

I put an illustration online:
http://www.spinsister.nl/zandbak/filmpjes/jumpy.htm
(You may have to scroll down a bit.)


Any idea how I can tame the pop ups to pop up in the middle?

--
Regards,
Adriana.
[ put out the rubbish if you need to reach me by e-mail ]
www.spinsister.nl

A.Translator