There doesn't seem to be a line 36 in naslovna.xhtml. There must be a more verbose option to tell you what resource is causing the problem.
How are you checking this as most checkers need an online version to check properly? I couldn't see an option for testing local sites.
I can't really see what its complaining about apart from the font files I mentioned before.
Sorry but speed optimisation is not really a CSS issue as such and an in depth analysis is probably beyond me apart from the obvious problems.