apache が止まっていたので調べてみた．
% sudo service apache2 start Starting web server: apache2 failed! The apache2 configtest failed. ... (warning). Output of config test was: AH00526: Syntax error on line 1 of /etc/apache2/conf-enabled/javascript-common.conf: Invalid command 'Alias', perhaps misspelled or defined by a module not included in the server configuration Action 'configtest' failed. The Apache error log may have more information.
とのことで，http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=711925 の症状らしい．
そもそも jQuery とかも使っていないので javascript-common 自体が不要な気がするが，
% sudo a2enmod alias % sudo service apache2 start
で復帰．