Good evening, I wanted to offer my congratulations for this beautiful theme. (easy, light and FAST)
I apologize if I make a trivial question for you:
I have a domain hosted on a shared server I'm trying to optimize,
and I used gmetrix for an assessment,
which gives me this is the result:
I just installed the theme (I do not use plugins)
thank you, that's all.

• YSlow
Use efficient CSS selectors | F(0)
http://pastebin.com/iCs3UQHK

you know how I can fix this?

You could try some of the settings in the various CSS sections of the theme options but frankly I never pay much attention to the "optimizing" tools out there. The only thing I do is perhaps add a caching plugin.