Last modified: 2011-09-21 13:26:51 UTC
Pages "&", "&a", "&am", "&" produce the expected "article not found" page. Pages "©", "<", ">", """ produce the expected "bad title" page. Page "&" produces an error page with the following footer: --- If you report this error to the Wikimedia System Administrators, please include the details below. Request: GET http://en.wikipedia.org/wiki/&, from 67.188.136.234 via sq73.wikimedia.org (squid/2.7.STABLE9) to () Error: ERR_ACCESS_DENIED, errno [No Error] at Wed, 21 Sep 2011 06:44:20 GMT ---
It's intended. It blocks bad spiders and other broken bots efficiently.