LJ Layout Question

[switch842]

I was thinking it might be nice to add some sort of visual break between the entries on my LJ. Just like a simple break line. But I have no idea where to look in the code to see if it's something I can just tweak, or if it's a whole new chunk of code I would have to add. In which case, how the hell do I do that? THIS is my layout if anyone might be willing to take a look at the CSS and let me know if this is possible.

Thanks!