offer an explain to manual error

git-svn-id: http://hustoj.googlecode.com/svn@2151 19ab8b60-bd6c-11dd-baed-41e496641fac
explain field

git-svn-id: http://hustoj.googlecode.com/svn@2152 19ab8b60-bd6c-11dd-baed-41e496641fac