gnome window placement (particularly iceweasel)

[michael <cs@networkingnewsletter.org.uk>]

Howdy folks,
I recently upgraded from Etch to Lenny on amd64. I notice that now some
windows change their position particularly iceweasel. I have 4
workspaces and 2 monitors (and use nVidia's own driver). The two
"features" I've noticed but wish to control are

a) if iceweasel starts on the right hand monitor it automatically moves
to the left hand monitor

b) if iceweasel is already running in the top-left workspace and
Evolution in the bottom-left, then clicking on a hyperlink in an email
results in the iceweasel window moving to the bottom-left window

I've looked around but can't see where this (new) behaviour is set.

Thanks in adv, M