goffice should adopt a standard capitalization of the ID abbreviation.

Note the first line if the PO file is:

../goffice/app/file.c:473
ID

whereas there are inconsistent abbreviations thereafter in the PO file.  Even though these may refer to different types of ID, consistency in the abbreviation of ID would be desirable and the type of ID being referenced is implied by the context of the string.

Lower case "id" is a concept from Freudian psychology.
http://en.wikipedia.org/wiki/Id,_ego_and_super-ego

../goffice/app/go-plugin.c:360
File contains plugin info with invalid id (%s), expected %s.

../goffice/app/go-plugin.c:858
Errors while reading services for plugin with id="%s".

../goffice/app/go-plugin.c:870
Plugin id contains invalid characters (%s).

../goffice/app/go-plugin.c:878
No loader defined or loader id invalid for plugin with id="%s".

../goffice/app/go-plugin.c:884
Plugin has no id.

../goffice/app/go-plugin.c:980
Couldn't activate plugin with id="%s".

../goffice/app/go-plugin.c:986 
../goffice/app/go-plugin.c:1164
Couldn't find plugin with id="%s".

../goffice/app/go-plugin.c:1158
Couldn't load plugin with id="%s".
  
../goffice/graph/gog-axis-line.c:704
Cross axis id


These are ok:

../goffice/app/go-plugin.c:1480
Couldn't activate plugin "%s" (ID: %s).

../goffice/app/go-plugin.c:1515
Couldn't deactivate plugin "%s" (ID: %s).

../goffice/graph/gog-object.c:679
Object ID

../goffice/graph/gog-object.c:680
Object numerical ID