It's after the main content. Works correctly in Firefox Beta 11. Broken in Aurora 12.
After running the mozregression tool. Last good nightly: 2011-08-21 First bad nightly: 2011-08-22 Pushlog: http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=6dc468c41136&tochange=f41df039db03
Oh, taintEnabled. This is a known bug with old MediaWiki version browser-sniffing code. The site needs to be fixed...
I opened a bug report on their system: http://wikitravel.org/shared/Tech:Left_column_problem_in_latest_Firefox
Declared fixed on their Web site