Opening windows at a default location

[ACario]

Hi,

I hope everything works fine for you all.

I'd like to get newly opened windows positioned at a default location
that is not the top left corner of the screen. I know of the
"-geometry" option for some apps such as a Gnome-terminal, but I'm 
looking for an option that would work with Mozilla Thunderbird
or Firefox.

Thanks in advance for your help, and happy Linux hacking.

Adam