Exclude several titles and headers

Hi Team, I really hope you can help me out here, I´m trying to hide some titles from the content site in the middle with custom CSS, but once one title is gone something different changes. Or it is not hiding at all. In example i try to hide comments-title from this page: http://s2.isqueen.de/%d0%be%d1%82%d0%b7%d1%8b%d0%b2%d1%8b/ The following command in CSS is written: #comments-title{display:none;} But nothing happens... Or I try to remove the category title from this page: http://s2.isqueen.de/category/%d0%b0%d0%b2%d1%82%d0%be%d1%80/ with the follwoing command: .page-header{display:none;} Also nothing happens... Basically what I try to do is to bring the content from the middle on the same level as the button on the left side from the side menu. So that everything under the main menu is on the same level, also the search bar. Could you take a look at say what is going wrong? Regards Alex