diff --git a/isso/js/app/api.js b/isso/js/app/api.js
index e4f0118..24de165 100644
--- a/isso/js/app/api.js
+++ b/isso/js/app/api.js
@@ -47,7 +47,11 @@ define(["app/lib/promise"], function(Q) {
                 document.cookie = cookie;
             }
 
-            resolve({status: xhr.status, body: xhr.responseText});
+            if (xhr.status >= 500) {
+                reject(xhr.body);
+            } else {
+                resolve({status: xhr.status, body: xhr.responseText});
+            }
         }
 
         try {
@@ -88,7 +92,13 @@ define(["app/lib/promise"], function(Q) {
     var modify = function(id, data) {
         var deferred = Q.defer();
         curl("PUT", endpoint + "/id/" + id, JSON.stringify(data), function (rv) {
-            deferred.resolve(JSON.parse(rv.body));
+            if (rv.status === 403) {
+                deferred.reject("Not authorized to modify this comment!");
+            } else if (rv.status === 200) {
+                deferred.resolve(JSON.parse(rv.body));
+            } else {
+                deferred.reject(rv.body);
+            }
         });
         return deferred.promise;
     };
diff --git a/isso/js/app/lib/promise.js b/isso/js/app/lib/promise.js
index a540c56..4f23be9 100644
--- a/isso/js/app/lib/promise.js
+++ b/isso/js/app/lib/promise.js
@@ -2,6 +2,8 @@ define(function() {
 
     "use strict";
 
+    var stderr = function(text) { console.log(text); };
+
     var Promise = function() {
         this.success = [];
         this.errors = [];
@@ -12,7 +14,7 @@ define(function() {
         if (onError) {
             this.errors.push(onError);
         } else {
-            this.errors.push(console.log);
+            this.errors.push(stderr);
         }
     };