Remove borders around background images in toolbar..

I'm using RH8 in Win 7 to output webhelp, and I'm creating a new skin. I've used the Webhelp skin editor to add button images and a toolbar background. But after generation, if the browser is resized to > the image width then the image repeats and the join between them is obvious:

I'm guessing that this is a css setting somewhere, but I don't know where.

I also want to remove the gap between the button images, and assume that there's a css tweak that can do that to.

Does anyone know how these borders and gaps can be removed?

Thanks