You screenshots are in a poor quality so I don't see that much.
However I think it'squite easy to solve. As I said, use firebug to find the ID of the div you want to customize. The ID is something unique so it any rule made on this ID will be applied only on ONE element, I think that's what you need
.
I guess you are currently applying your modification on the class of the element which is also present on multiple elements, explaining why your modification is visible in different places.
I hope it helped.