Issue with nav header conflicting with changes to child theme

Hey guys, in reference to this link:http://wordpress.org/support/topic/place-nav-bar-underneath-header-image-on-twenty-twelve-theme

I created the child theme with a header.php but it didn’t add my header image above the nav.

I’m guessing because there’s conflict with my child theme style.css:

//*
Theme Name:Twenty Twelve Child
Version: 1.0
Theme URI: http://quirm.net/themes
Description: A basic starter child theme for Twenty Twelve
Author: Mel Pedley
Author URI: http://blackwidows.co.uk
Template: twentytwelve
License: GNU General Public License v2
License URI: http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
*/

/* Import layout */
@import url(../twentytwelve/style.css);

.main-navigation ul.nav-menu {
 text-align: center;
}

body .site {
padding: 0 40px;
padding: 0 2.857142857rem;
margin-top: 0px;
margin-bottom: 48px;
margin-bottom: 3.428571429rem;
box-shadow: 0 2px 6px rgba(100, 100, 100, 0.3);
}
.entry-content img, .comment-content img, .widget img, img.header-image, .author-avatar img, img.wp-post-image {
    border-radius: none !important;
    box-shadow: none !important;
}

.entry-meta {
   display: none;
}

.entry-header {
    display: none;
}

.site-content {
margin-top: 2px !important;
}

.widget-area {
margin: 2px 0 0;
}

.site-header {
padding: 1.71429rem 0 14px;
}

<meta name="viewport" content="width=1100px, initial-scale=1, maximum-scale=1">