Today, I was quite excited to activate the WordPress Twenty Thirteen Theme (WP 3.6), but had to deactivate it immediately because the sidebar flowed below the footer on short pages. This was rather embarrassing.
I hope there's a way out of this flaw, because the Theme promises to be a great improvement on previous themes by WordPress. I reverted back to WordPress Twenty Eleven Theme, which has no such problem.
I just visited the website of one of the reviewers below and found an example of this problem at http://amsyong.com/daftar-isi/
It's a serious flaw.