Theme 'Twenty Ten' sidebars pushed to left and bottom.

My secondary sidebar (secondary widget area) is being pushed to the bottom of my page and I can’t seem to fix it. The primary widget area with the search form is spaced to the left and that’s not right too.

See here: https://www.dutchlabel.nl/blog/

I’ve found two topics concerning this problem:
1. https://www.ads-software.com/support/topic/my-sidebar-is-at-bottom-of-screen-why?replies=15
2. https://www.ads-software.com/support/topic/sidebar-content-pushed-to-bottom-of-page?replies=14
But possible solutions given in both topics don’t work for me.

Can someone help?