Adjust width?

Hi.
I really like this theme. It is clean and have nice menus for those who use mobile phones so they easily can access submenus. And the front picture have a decent size.

But how do I adjust page width?
I tried with this:

#page {max-width: 70%;}
.entry-title {display: none;}

But then the page isnt centered anymore, it have moved a little bit to the left.