Playing with CSS

I like the Oil Drum's style of displaying discussion threads. I thought I would try to reproduce it. I'm doing the unorthodox thing of using custom tags instead of custom classes, just to save typing. (I'm not using Zen Coding to write my HTML, so I can't just write div.oildrum>div.post+div.replies>div.post*2 and div.post+div.replies>div.post+div.replies>div.post and div.post to build the structure. Besides, the HTML is more readable this way.) This is a post. This is one reply. This is another reply. Here's another top-level post. Here's a reply to it. This reply is a bit longer, in order to show what happens when the text wraps a little bit. And here's a reply to that. And another reply to the top-level post.