When I mean CSS I mean using:
Code:
body {background-img:url("yourbgimg.gif");
background-attachment:fixed;}
In the headinclude template you said. IIRC You can't use the background-attachment:fixed; if you are using <body background="yourbgimg.gif">
And yes, it stops the image from moving along with the rest of the page (I believe it's popular with people who use blogs)