yes, the method i said was incorrect as i though you were trying to change the titles.
It is the smallfont as lynne says, but if you change the smallfont size it will change all the times the smallfont is called, your best bet would be to create a custom CSS definition and change "smallfont" to your custom CSS, if you need additional help as lynne suggests please show the HTML comments by,
admincp > vboptions > General Settings > Add Template Name in HTML Comments > set to Yes
then provide a link your forum