Not in the CSS but in the HTML code of your root gallery you'd find it
But, like I said, my project is different so I have created a place holder (the frame) of my slideshow with proper size.
The code I used is
<TD align=center>
<img border="3" src="http://www.pbase.com/imageaddress/medium.jpg" width="400" height="267" id="Placeholder0"></TD>
As you can see I have put it in the center of my root page and the place holder source has the address of first image to produce
Anyway I think it is better for you to ask Luis for a support as wel
Massimiliano