I looked at his source code and noticed that it’s images used to create the box. Take a look at his source code for youself and you’ll see he’s using these images called “dot_clear.gif” and “dot_back_green.gif”. He used them in a table to have it look like that.
Might I add that you can do something similar with css however the dots will not be that fine. Also he mad a thin 1 px And the image is a background image with a y repeat css style attribute. But then again you probably knew that. If you need help with pulling this off in css let me know