CSS Repeat the background from a particular point

CSS Repeat the background from a particular point

I want the background to be displayed from the line drawn on the screenshot:
http://img29.imageshack.us/img29/4707/wjm7.png
I tried to use
background : ('path/to/image') 0 650px repeat-y
But it the light part of the image moves and it looks ugly. All I want is
simply to background look on the site like on the screenshot, but without
the dark part in the bottom. Thats why I want it to repeat from the red
line.
Now the css is this way:
background : url('path/to/image') top center