Why do some posts show up in bold while others do not?

[KidsHappen]

From what I can tell it doesn't seem to be related to if you have read them or not.

[Sunny]

Your're right. Ive noticed it has nothing to do with today vs. yesterday, or whether they have been read or not read. WHAT does it mean??

[Janna]

I thought it had to do with whether a new post was added to it? Which is why the bold ones are usually on the first page. I've noticed that the ones that aren't in bold on the first page, are the ones I've read. Maybe I'm wrong though.

[LaMere Academy]

bold should be ones with new posts, that you haven't read yet.
unbold will be ones you've read or posted on and nothing new has been posted since.

I think that's right :D