Centering content on homepage (blogpage)

Hello,

I am working with the theme Masonic. Very greatfull for this very nice template. I am adjusting it to my own taste, but ran into a problem.

I have centered all static pages:

.primary {
	float: none;
	margin-right: 4%;
	width: 75%; 
	margin: 0 auto;

Now I am trying to center the blog-page as well (home-page). However, my code is overruled by something I can’t find. Would someone be able to help me out?

.post-container {
	width: 75%;
	float: none;
	margin: 5px auto !important;
}