Write page on Sparkle update errors that can happen if you’re running the app from the ~/Downloads folder.

Technotes/SparkleUpdateError.markdown

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+# “Can’t Update” Error
+
+If NetNewsWire’s auto-updater gives you an error that it can’t be updated, do this:
+
+* Cancel the update if you still need to
+* Quit NetNewsWire
+* Move NetNewsWire to your Applications folder (or to your `~/Applications/` folder)
+* Launch NetNewsWire
+* Check for Updates again
+
+That should do the trick!
+
+## The problem
+
+If you’re running the app from your `~/Downloads` folder, then the system has placed your app under quarantine — which means the app can’t update itself.
+
+Once you move the app to another folder, the quarantine is lifted, and the app can update itself.
+
+This *does* require your manual intervention: it‘s not something NetNewsWire can do for you automatically.
+
+For more info, [see this bug](https://github.com/brentsimmons/NetNewsWire/issues/213).