POST caught errors to me.

lib/$.coffee

@@ -41,10 +41,10 @@ $.extend $,
         fd.append key, val
     fd
   ajax: (url, callbacks, opts={}) ->
-    {type, headers, upCallbacks, form} = opts
+    {type, headers, upCallbacks, form, sync} = opts
     r = new XMLHttpRequest()
     type or= form and 'post' or 'get'
-    r.open type, url, true
+    r.open type, url, if sync then false else true
     for key, val of headers
       r.setRequestHeader key, val
     $.extend r, callbacks

src/features.coffee

@@ -3517,7 +3517,6 @@ ExpandThread =
     threadRoot = thread.OP.nodes.root.parentNode
     a = $ '.summary', threadRoot
 
-
     switch thread.isExpanded
       when false, undefined
         thread.isExpanded = 'loading'

src/main.coffee

@@ -527,7 +527,7 @@ Main =
         new Notification 'info', el, 120
 
   handleErrors: (errors) ->
-    unless 'length' of errors
+    unless errors instanceof Array
       error = errors
     else if errors.length is 1
       error = errors[0]
@@ -538,12 +538,10 @@ Main =
     div = $.el 'div',
       innerHTML: "#{errors.length} errors occurred. [<a href=javascript:;>show</a>]"
     $.on div.lastElementChild, 'click', ->
-      if @textContent is 'show'
-        @textContent = 'hide'
-        logs.hidden  = false
+      [@textContent, logs.hidden] = if @textContent is 'show'
+        ['hide', false]
       else
-        @textContent = 'show'
-        logs.hidden  = true
+        ['show', true]
 
     logs = $.el 'div',
       hidden: true
@@ -553,14 +551,30 @@ Main =
     new Notification 'error', [div, logs], 30
 
   parseError: (data) ->
-    {message, error} = data
-    c.error message, error.stack
+    Main.logError data
     message = $.el 'div',
-      textContent: message
+      textContent: data.message
     error = $.el 'div',
-      textContent: error
+      textContent: data.error
     [message, error]
 
+  errors: []
+  logError: (data) ->
+    unless Main.errors.length
+      $.on window, 'unload', Main.postErrors
+    c.error data.message, data.error.stack
+    Main.errors.push data
+
+  postErrors: ->
+    errors = Main.errors.map (d) -> d.message + ' ' + d.error.stack
+    $.ajax '<%= meta.page %>errors', {},
+      sync: true
+      form: $.formData
+        n: "<%= meta.name %> v#{g.VERSION}"
+        t: '<%= type %>'
+        ua: window.navigator.userAgent
+        e: errors.join '\n'
+
   isThisPageLegit: ->
     # 404 error page or similar.
     unless 'thisPageIsLegit' of Main