Anyone know how he structured his posts in sidebar?

Hi folks

Please check this site- htmldog.com

If you click on the links at left, you'll see more sub categories (if you say so). Interesting thing is if you click on any category/ sub category you'll see an article appears instead of showing lists of posts that we see in the normal wordpress sites.

I'm thinking how to add posts so that I get this structure?

Your input is highly appreciated.
webn

 

I don't think he is using posts/categories. I would do this using child/parent pages.