Page wrap is not centered

Hi. I’m having a CSS problem on my site http://daytodayphoto.com/

To center the page in CSS, I apply a margin: 0 auto; to the div #page-wrap. This works well on every page except on the archives page such as http://daytodayphoto.com/category/features . On this page, #page-wrap seems to have a fixed left margin and variable right margin, but when i look at the code, the margin is still 0 auto.

I’m completely puzzled. Please help. Thanks