Zen Minimum Theme

I have spent several days combing through my stylesheet and other files to find how to chage the font size of my actual post. No matter what I change, the font in the post area refuses to change size (though I seem to be able to increase the font weight). I seem to have no problem with any other area of the blog, only the post, which to me is the most important area in which to maintain some degree of control!
The site where I am having the problem is located at http://www.thelazeist.com/blog/ so if someone who knows php could take a look, maybe in one simple line (which I will be embarrassed to see how easy it really is!) it could be explained to me.
Thanks in advance for any help… this Lazeist is tired of shooting in the dark!