twenty eleven theme – issue with header

Hi. I have twenty eleven theme, newest version and it does not work well with NextGen gallery – the picture shown is “below” the header. I tried to change style.css of the theme, based on a discussion here:
http://ww.wp.xz.cn/support/topic/plugin-nextgen-gallery-images-appear-under-header?replies=16#post-2508168
But no help…

Thank you.

http://ww.wp.xz.cn/plugins/nextgen-gallery/