Cindy's quite right to start off with the basics on a problem like this.. it's often something pretty rudimentary, although it can seem quite baffling at the time! One thing I noticed immediately from looking at your source code was that you're referencing a local file which I imagine is stored on your PC (see below)
background-image: url(file:///C:/knlst/bground.jpg);
whereas the the file's actual location on your site is here -
http://www.kneelsit.com/bground.jpg
Try adjusting your code accordingly, and see if this improves matters.
Paul