Border-bottom below every post

Hi,
I beg for your urgen help.
Does anybody know how to add border-bottom (1 px dotted line) after every post in the list? I’ve tried to modify css class .scu-clear and got a lot of border lines around the post. 🙂

I hope, somebody can explain where and what to modify (add or smth). Thanks in advance.

http://ww.wp.xz.cn/extend/plugins/site-creator-ultimate/