Image Viewer doesnt resize in Firefox

Hello,

I am trying to use the image viewer in Dreamweaver MX and having a
problem. It works fine except when viewing in Firefox it only shows in
it's default 400x325 size. I have tried resizing it everyway possible
and Firefox just doesn't seem to take to it. The source images are
660x480. A sample of it is here http://www.helixe.com/sw-manual.htm

Any pointers would be appreciated.

Thanks