Images are lost

I have my site just about put together, and I have now moved all the images into the proper directories. My style sheets are all amended and (in TopStyle) are able to locate the images which are used at background images, without problem. However, when I test my pages in the browsers, none of my background images are appearing.. !! What's the issue here? If TopStyle is showing my images in the style preview window, why can't the browser seem to find them? :?