The Consular Electronic Application Center (CEAC) used to access forms DS-160, DS-260, payment of immigrant fees, check status of cases, etc., will be unavailable from 9:00 a.m. to 9:00 p.m. Eastern Standard Time (from 6:30 p.m. on April 29, 2017 to 6:30 a.m. on April 30, 2017 Indian Standard Time). The alert also indicates that the maintenance may extend beyond this time. This alert can be found here.
We recommend U.S. visa applicants to avoid accessing the system during this time.