iphone 5 突然無法登入facebook app及gmail app

如題，但若使用safari上facebook卻可登入,也重置遇網路設定,仍無效，請各位大大教我吧

用iFile打開/etc/hosts這個檔案,按下此檔案右邊的箭頭,跳出檔案屬性畫面時,在"開啟方式"按一下,選擇"純文字檢視器",打開後將內容改成以下文字即可,最後保存完重開機就OK了!!

# Host Database
# localhost is used to configure the loopback interface
# when the system is booting. Do not change this entry.

127.0.0.1 localhost
255.255.255.255 broadcasthost
::1 localhost
fe80::1%lo0 localhost