Step 1: open Cydia and tap the Manage tab at the bottom of the screen.
Step 2: tap Sources.
Step 3: tap Edit in the upper right-hand corner of the Sources page and then tap the red minus sign next to Dev Team and delete the Dev Team UltraSn0w repo (http://repo666.ultrasn0w.com).
Step 4: Tap Done in the upper right-hand corner.
Step 5: Tap the Changes tab at the bottom of the screen and tap the Refresh button in the upper left-hand corner to refresh your Cydia sources.
Step 6: You should notice that the errors from the UltaSn0w repo have stopped occurring.
And that’s all there is to it. Of course, adding UltraSn0w back is just as easy as removing it. Instead of using Edit > remove, just use Edit > Add on the Sources page, and type in UltraSn0w’s repo address.