When I first started getting my feet wet with web design and support, I had trouble understanding style sheets and how they worked. TopStyle Lite — the free, downsized version of TopStyle — was recommended to me as a good visualizing tool. And so it is. The nature of style sheets is evolving, but I still use TopStyle Lite pretty regularly for sites using standard style sheets.
Download a style sheet (css file) and open in it TopStyle Lite, and both seeing what you have and seeing where you’re going become really simple. Change the attribute on the right side of the screen, and TopStyle will change the related item in the style sheet. It’s nice until one gets comfortable with style sheets…and even beyond.