diff --git a/misc/ajax.js b/misc/ajax.js
index bb4a6e1..c944ebb 100644
--- a/misc/ajax.js
+++ b/misc/ajax.js
@@ -476,7 +476,7 @@ Drupal.ajax.prototype.getEffect = function (response) {
  * Handler for the form redirection error.
  */
 Drupal.ajax.prototype.error = function (xmlhttprequest, uri, customMessage) {
-  alert(Drupal.ajaxError(xmlhttprequest, uri, customMessage));
+  Drupal.displayAjaxError(Drupal.ajaxError(xmlhttprequest, uri, customMessage));
   // Remove the progress element.
   if (this.progress.element) {
     $(this.progress.element).remove();
diff --git a/misc/autocomplete.js b/misc/autocomplete.js
index d71441b..af09071 100644
--- a/misc/autocomplete.js
+++ b/misc/autocomplete.js
@@ -310,7 +310,7 @@ Drupal.ACDB.prototype.search = function (searchString) {
         }
       },
       error: function (xmlhttp) {
-        alert(Drupal.ajaxError(xmlhttp, db.uri));
+        Drupal.displayAjaxError(Drupal.ajaxError(xmlhttp, db.uri));
       }
     });
   }, this.delay);
diff --git a/misc/drupal.js b/misc/drupal.js
index 427c4a1..af3de30 100644
--- a/misc/drupal.js
+++ b/misc/drupal.js
@@ -414,6 +414,29 @@ Drupal.getSelection = function (element) {
 };
 
 /**
+ * Add a global variable which determines if the window is being unloaded.
+ *
+ * This is primarily used by Drupal.displayAjaxError().
+ */
+Drupal.beforeUnloadCalled = false;
+$(window).bind('beforeunload', function () {
+    Drupal.beforeUnloadCalled = true;
+});
+
+/**
+ * Displays a JavaScript error from an Ajax response when appropriate to do so.
+ */
+Drupal.displayAjaxError = function (message) {
+  // Skip displaying the message if the user deliberately aborted (for example,
+  // by reloading the page or navigating to a different page) while the Ajax
+  // request was still ongoing. See, for example, the discussion at
+  // http://stackoverflow.com/questions/699941/handle-ajax-error-when-a-user-clicks-refresh.
+  if (!Drupal.beforeUnloadCalled) {
+    alert(message);
+  }
+};
+
+/**
  * Build an error message from an Ajax response.
  */
 Drupal.ajaxError = function (xmlhttp, uri, customMessage) {