Small Titles Shown when I scroll down?

Hmm, yesterday I wanted to install the ‘related posts’ plugin, but that didn’t worked properly. Anyway, I deactivated the plugin, but now I encountered the following problem.

Go to my blog http://www.xternall.com and look at the Title per post.

Now scroll down a bit, and as you can see the Title post suddenly appears smaller! Here is a screenshot (click here)

How is this possible?

Thanks.