Posts are Slightly Off Center

Hello,

I’ve been reading through the forums, and I seem to have a similar problem with centering images in my slideshow that many others have had.

My wordpress theme is 850 pixels wide, so I created jpgs that were this wide. But for some reason, when I create a gallery the images are all just SLIGHTLY too far to the right, and it looks strange:

http://actionathena.com/action-athena-comics/

I tried using the following basic centering code:

<center>[portfolio_slideshow id=5433]</center>

…but that has only centered the text to navigate through the slideshow, not the images.

I’m not sure where I should go to edit this code. Any help would be much appreciated. Thanks!

http://wordpress.org/extend/plugins/portfolio-slideshow/