Changing font size

Hi,

I want to change the font size here:

http://www.thegunandsportshop.co.uk/main.php

Everywhere I've tried on the 'theme.css' hasn't worked. The text should be the same as http://www.thegunandsportshop.co.uk/index.html. This is controlled from a different stylesheet, but I've appended theme.css with the required styling from the existing stylesheet. I can't work out where the style being applied is coming from so I can change it.

Any ideas?

Thanks,
Mart