The text "Main Page" in some language wikipedias appears as a broken text instead of a hyper link. Some script overwrites the vectorTab caption as plain text as opposed to be a hyper link.
Screenshot:- http://tawp.in/r/2bgy regarding the problem.
This bug is present in Tamil,Telugu wikipedias and other wiki-sister projects.
and possibly many more. However not all language Wikis have this problem, Malayalam and Bengali seems to work fine.