On the Opera mini browser, the sidebar menus are closed and cannot be expanded. This can be verified on the opera mini simulator - http://www.opera.com/mobile/demo/
Version: 1.16.x
Severity: enhancement
URL: http://en.wikipedia.org/wiki/Wikipedia:Requests_for_comment/May_2010_skin_change/Bug_reports#Expanding_left_menu_does_note_expand_in_Opera_Mini