THREAD TITLES.

I have always wondered this, and have not yet found a solution, so I thought to finally ask. Why do some thread titles come out bold, and some are a bit less bold? I am tired right now, so I am not going to post images, but what I am talking about is that the thread Illumia comes out bolder than the thread Red Alert coversion to C&C95. I don't know why, but ti does. Is it anything to do with me posting in the thread? Hopefully that was descriptive enough to get an answer, if not, I suppose I could put some pics up tomorrow, too tired tonight.