All posts change their background to black…!!!

Hi,
I have a problem with my wordpress blog, which I can’t understand… When I’m not loged in, the background of each post changes to very dark grey and the sidebar disappears… everything seems fine when I’m loged in the admin panel and was fine yesterday. I haven’t done any changes to anything since then. I really can’t understand what’s wrong… please help! The site is: affiliate-favorites.com

Thanks!