I saw there’s no option to change the font size of the post metas.
So I tried adding the font size of entry-meta to the custom CSS with no success. It just for get the settings, though, in firebug I can see that it is.
What’s the problem?
You can see example here: http://www.udiburg.com/blog10/
Some rules need to be more specific to apply.
If you have a custom rule that works in Firebug but not when placed in Custom CSS, add (for example) body in front of it to make it more specific.