diff --git a/src/General/Main.coffee b/src/General/Main.coffee
index ee2fd9381..179e80484 100755
--- a/src/General/Main.coffee
+++ b/src/General/Main.coffee
@@ -129,12 +129,14 @@ Main =
 
   initReady: ->
     if d.title in ['4chan - Temporarily Offline', '4chan - 404 Not Found']
-      if Conf['404 Redirect'] and g.VIEW is 'thread'
-        href = Redirect.to 'thread',
-          boardID:  g.BOARD.ID
-          threadID: g.THREADID
-          postID:   +location.hash.match /\d+/ # post number or 0
-        Redirect.navigate href, "/#{g.BOARD}/"
+      if g.VIEW is 'thread'
+        ThreadWatcher.set404 g.BOARD.ID, g.THREADID, ->
+          if Conf['404 Redirect']
+            href = Redirect.to 'thread',
+              boardID:  g.BOARD.ID
+              threadID: g.THREADID
+              postID:   +location.hash.match /\d+/ # post number or 0
+            Redirect.navigate href, "/#{g.BOARD}/"
       return
 
     # 4chan Pass Link
diff --git a/src/General/Settings.coffee b/src/General/Settings.coffee
index 0fbb11dd5..1518da3df 100755
--- a/src/General/Settings.coffee
+++ b/src/General/Settings.coffee
@@ -175,15 +175,17 @@ Settings =
     reader = new FileReader()
     reader.onload = (e) ->
       try
-        Settings.loadSettings JSON.parse e.target.result
-        if confirm 'Import successful. Reload now?'
-          window.location.reload()
+        Settings.loadSettings JSON.parse(e.target.result), (err) ->
+          if err
+            output.textContent = 'Import failed due to an error.'
+          else if confirm 'Import successful. Reload now?'
+            window.location.reload()
       catch err
         output.textContent = 'Import failed due to an error.'
         c.error err.stack
     reader.readAsText file
 
-  loadSettings: (data) ->
+  loadSettings: (data, cb) ->
     version = data.version.split '.'
     if version[0] is '2'
       convertSettings = (data, map) ->
@@ -265,11 +267,17 @@ Settings =
     if data.Conf['WatchedThreads']
       data.Conf['watchedThreads'] = boards: ThreadWatcher.convert data.Conf['WatchedThreads']
       delete data.Conf['WatchedThreads']
-    $.clear -> $.set data.Conf
+    $.clear (err) ->
+      return cb err if err
+      $.set data.Conf, cb
 
   reset: ->
     if confirm 'Your current settings will be entirely wiped, are you sure?'
-      $.clear -> window.location.reload() if confirm 'Reset successful. Reload now?'
+      $.clear (err) ->
+        if err
+          $('.imp-exp-result').textContent = 'Import failed due to an error.'
+        else if confirm 'Reset successful. Reload now?'
+          window.location.reload()
 
   filter: (section) ->
     $.extend section, <%= importHTML('Settings/Filter-select') %>
diff --git a/src/General/lib/$.coffee b/src/General/lib/$.coffee
index 3df85540c..5250c132e 100755
--- a/src/General/lib/$.coffee
+++ b/src/General/lib/$.coffee
@@ -361,16 +361,16 @@ do ->
     chrome.storage.sync.remove keys
 
   timeout = {}
-  setArea = (area) ->
+  setArea = (area, cb) ->
     data = {}
     $.extend data, items[area]
     return if !Object.keys(data).length or timeout[area] > Date.now()
     chrome.storage[area].set data, ->
-      if chrome.runtime.lastError
-        c.error chrome.runtime.lastError.message
+      if err = chrome.runtime.lastError
+        c.error err.message
         setTimeout setArea, $.MINUTE, area
         timeout[area] = Date.now() + $.MINUTE
-        return
+        return cb? err
 
       delete timeout[area]
       delete items[area][key] for key of data when items[area][key] is data[key]
@@ -382,29 +382,32 @@ do ->
           delete $.localKeys[key]
           key
         chrome.storage.local.remove oldLocal
+      cb?()
 
   setSync = $.debounce $.SECOND, ->
     setArea 'sync'
 
-  $.set = (key, val) ->
-    data = if typeof key is 'string'
-      $.item key, val
+  $.set = (key, val, cb) ->
+    if typeof key is 'string'
+      data = $.item key, val
     else
-      key
+      data = key
+      cb = val
     $.extend items.local, data
     $.localKeys[key] = true for key of data
-    setArea 'local'
+    setArea 'local', cb
 
   $.clear = (cb) ->
     items.local = {}
     items.sync  = {}
     $.localKeys = {}
     count = 2
+    err   = null
     done  = ->
       if chrome.runtime.lastError
         c.error chrome.runtime.lastError.message
-        return
-      cb?() unless --count
+      err ?= chrome.runtime.lastError
+      cb? err unless --count
     chrome.storage.local.clear done
     chrome.storage.sync.clear  done
 <% } else { %>
@@ -470,13 +473,14 @@ $.set = do ->
       # for `storage` events
       localStorage.setItem key, val
 
-  (keys, val) ->
+  (keys, val, cb) ->
     if typeof keys is 'string'
       set keys, val
-      return
-    for key, val of keys
-      set key, val
-    return
+    else
+      set key, value for key, value of keys
+      cb = val
+    cb?()
+
 $.clear = (cb) ->
   try
     $.delete GM_listValues().map (key) -> key.replace g.NAMESPACE, ''
diff --git a/src/General/lib/databoard.class b/src/General/lib/databoard.class
index 3b4eccbae..84b0db994 100755
--- a/src/General/lib/databoard.class
+++ b/src/General/lib/databoard.class
@@ -13,7 +13,7 @@ class DataBoard
       @sync = sync
     $.on d, '4chanXInitFinished', init
 
-  save: -> $.set @key, @data
+  save: (cb) -> $.set @key, @data, cb
 
   delete: ({boardID, threadID, postID}) ->
     $.forceSync @key
@@ -38,7 +38,7 @@ class DataBoard
     else unless Object.keys(@data.boards[boardID]).length
       delete @data.boards[boardID]
 
-  set: ({boardID, threadID, postID, val}) ->
+  set: ({boardID, threadID, postID, val}, cb) ->
     $.forceSync @key
     if postID isnt undefined
       ((@data.boards[boardID] or= {})[threadID] or= {})[postID] = val
@@ -46,7 +46,7 @@ class DataBoard
       (@data.boards[boardID] or= {})[threadID] = val
     else
       @data.boards[boardID] = val
-    @save()
+    @save cb
 
   get: ({boardID, threadID, postID, defaultValue}) ->
     if board = @data.boards[boardID]
diff --git a/src/Monitoring/ThreadWatcher.coffee b/src/Monitoring/ThreadWatcher.coffee
index 1cee9b1fb..c9a5df82a 100755
--- a/src/Monitoring/ThreadWatcher.coffee
+++ b/src/Monitoring/ThreadWatcher.coffee
@@ -335,6 +335,17 @@ ThreadWatcher =
     else
       ThreadWatcher.refresh()
 
+  set404: (boardID, threadID, cb) ->
+    return cb() unless data = ThreadWatcher.db?.get {boardID, threadID}
+    if Conf['Auto Prune']
+      ThreadWatcher.db.delete {boardID, threadID}
+      return cb()
+    return cb() if data.isDead and not (data.unread? or data.quotingYou?)
+    data.isDead = true
+    delete data.unread
+    delete data.quotingYou
+    ThreadWatcher.db.set {boardID, threadID, val: data}, cb
+
   toggle: (thread) ->
     boardID  = thread.board.ID
     threadID = thread.ID