Actually if you use the code:
Code:
background-image: url(images/gradient.jpg);
it will pull it from the /skin1/images/ directory becuase it is a relative link and the CSS file is loading from that directory.
If your image is truely located at
http://www.sellproinc.com/images/gradient.jpg then you need to use the code:
Code:
background-image: url(/images/gradient.jpg);
so that it will look for the image in the directory off of the root