I had noticed those blue dots, but never got to understand what they mean. I opened one with blue dot and one without, I compared the two pages and I still didn't find an answer. I read GitHub's help, but nothing relates to my question.

So, I fired up FireBug and read the class. Luckily, GitHub web developer gave it a meaningful name instead of something like blue-dot.

Sometimes, RTFM doesn't work and you don't want to post a question like this, then you got to get creative. :)