[SOLVED] Problem with background showing up only on main page

Hey, I got a problem with my background image, it is only showing up on the main page...as soon as you click on the title of a post it is gone. What can I do, I put the url to the background image in the body style part, as such:

background: url(wp-content/themes/atahualpa333/images/background2.jpg)repeat top left;

Here is a link to my homepage:

http://www.ars-virtualis.com/ (no problem with b/g)

http://www.ars-virtualis.com/index.p...projektstelle/ (b/g not showing)

Thank you very much