RegDCP - 3:50 pm on Sep 17, 2012 (gmt 0)
I was incorrect.
It is a h4 that is the same size as standard bold. (Assuming a 12pt font size.)
The h tags are markup that Google uses to determine the importance of text.
I would think that the relative text sizes must be kept in proportion with h1 being the largest, h2 the next largest and so on.