BuddyPress.org

PS.:

margin: 0 9.46429%;

I guess, it’s not the reason for the misfuncting; but however – due to other theme modifications (https://wordpress.org/support/topic/making-a-better-usage-of-my-blog-space?replies=2#post-6034077) – I should choose 2.5% (instead of 9.46429), isn’t it?