kama inadai hiyo CardDAV password (ni email account ya yahoo) ina maana huwezi kuizima coz ukishikilia button ya power haikuruhusu inadai password, sio?? if so itabidi ureset your ipad kidogo kwa kupress and hold the Home and Sleep buttons simultaneously ignoring the red slider until the Apple logo appears. Let go of the buttons and let the iPad restart.
baada ya hapo ipad yako itakuwa imewaka fresh ila ukijaribu kufungua email, lile shida la mwanzoni litarudi,therefore, before you do anything else, go to Settings and tap Mail, Contacts, Calendars. Then delete your email account from there. unaweza add back ur yahoo email lakini uwe makini ukitumia your yahoo email adress especialy kama ina sync ur data as itakuwa inadai password kila ukigusa net
p.s, hakikisha umeback up vitu vyako vilivyopo kwa ipad yako kwa pc yako kabla hujareset as you stand to lose everything
regards, **leh