Hi,
As you might read on Wikitech-l, document.write is unsupported now in community and personal javascripts. Although at the end they decided not to make Wikipedia totally unreachable for users with such codes, :-) it is still a problem.
I wrote a quick and ugly script to warn these users: https://hu.wikipedia.org/wiki/Szerkeszt%C5%91:BinBot/documentwritewarning.py