Last modified: 2014-02-12 23:53:48 UTC
This happened after merging 0cfeb1f (Maintenance: Load minimum possible css / reorg css): https://gerrit.wikimedia.org/r/#/c/53627/ Since it is styled correctly in Chrome, I'm afraid it's again a Resource Loader problem.
This works for me.. even with debug=true applied...
Some other change must have fixed it.