diff --git a/seahub/templates/js/templates.html b/seahub/templates/js/templates.html
index 136a365bdc..8a62e33bc2 100644
--- a/seahub/templates/js/templates.html
+++ b/seahub/templates/js/templates.html
@@ -813,11 +813,11 @@
         </select>
     </td>
 </script>
-<script type="text/template" id="activity-group-tmpl">
-    <div>
-        <h4 class="activity-group-hd"><%= date %></h4>
-        <ol class="activity-group-bd"></ol>
-    </div>
+<script type="text/template" id="activity-group-hd-tmpl">
+    <h4 class="activity-group-hd"><%= date %></h4>
+</script>
+<script type="text/template" id="activity-group-bd-tmpl">
+    <ol class="activity-group-bd"></ol>
 </script>
 <script type="text/template" id="activity-item-tmpl">
     <%= activity.avatar %>
diff --git a/seahub/views/ajax.py b/seahub/views/ajax.py
index c5e42e357d..6f26f1a355 100644
--- a/seahub/views/ajax.py
+++ b/seahub/views/ajax.py
@@ -1913,14 +1913,18 @@ def repo_history_changes(request, repo_id):
 
     repo = get_repo(repo_id)
     if not repo:
-        return HttpResponse(json.dumps(changes), content_type=content_type)
+        err_msg = _(u'Library does not exist.')
+        return HttpResponse(json.dumps({'error': err_msg}),
+                status=400, content_type=content_type)
 
     # perm check
     if check_repo_access_permission(repo.id, request.user) is None:
         if request.user.is_staff is True:
             pass # Allow system staff to check repo changes
         else:
-            return HttpResponse(json.dumps(changes), content_type=content_type)
+            err_msg = _(u"Permission denied")
+            return HttpResponse(json.dumps({"error": err_msg}), status=403,
+                            content_type=content_type)
 
     username = request.user.username
     try:
@@ -1932,11 +1936,15 @@ def repo_history_changes(request, repo_id):
     if repo.encrypted and \
             (repo.enc_version == 1 or (repo.enc_version == 2 and server_crypto)) \
             and not is_passwd_set(repo_id, username):
-        return HttpResponse(json.dumps(changes), content_type=content_type)
+        err_msg = _(u'Library is encrypted.')
+        return HttpResponse(json.dumps({'error': err_msg}),
+                            status=403, content_type=content_type)
 
     commit_id = request.GET.get('commit_id', '')
     if not commit_id:
-        return HttpResponse(json.dumps(changes), content_type=content_type)
+        err_msg = _(u'Argument missing')
+        return HttpResponse(json.dumps({'error': err_msg}),
+                            status=400, content_type=content_type)
 
     changes = get_diff(repo_id, '', commit_id)
 
diff --git a/static/scripts/app/views/activities.js b/static/scripts/app/views/activities.js
index 4af5180235..eacc3e0b58 100644
--- a/static/scripts/app/views/activities.js
+++ b/static/scripts/app/views/activities.js
@@ -12,11 +12,8 @@ define([
 
         el: $('#activities'),
 
-        activityGroupTemplate: _.template($('#activity-group-tmpl').html()),
-
-        events: {
-            'click #activities-more': 'getMoreActivities'
-        },
+        activityGroupHdTemplate: _.template($('#activity-group-hd-tmpl').html()),
+        activityGroupBdTemplate: _.template($('#activity-group-bd-tmpl').html()),
 
         initialize: function () {
             this.activities = new ActivityCollection();
@@ -28,6 +25,10 @@ define([
             this.moreOffset = 0;
         },
 
+        events: {
+            'click #activities-more': 'getMoreActivities'
+        },
+
         getMoreActivities: function () {
             var _this = this;
             this.$loadingTip.show();
@@ -56,18 +57,20 @@ define([
                 allActivities = allActivities.concat(activitiesJson[i]['events']);
             }
 
+            // return sth. like {2015-07-27: [{...},], 2015-06-04: [{...}] ...}
             var groupedActivities = _.groupBy(allActivities, 'date');
 
+            var $groupDate, $groupActivities;
             for (var date in groupedActivities) {
-                var $activityGroup = $(this.activityGroupTemplate({'date': date})),
-                    activityList = groupedActivities[date];
+                $groupDate = $(this.activityGroupHdTemplate({'date': date}));
+                $groupActivities = $(this.activityGroupBdTemplate());
 
-                this.$activitiesBody.append($activityGroup);
-
-                _.each(activityList, function (activity) {
+                _.each(groupedActivities[date], function(activity) {
                     var view = new ActivityItemView(activity);
-                    $activityGroup.children('ol').append(view.render().el);
+                    $groupActivities.append(view.render().el);
                 });
+
+                this.$activitiesBody.append($groupDate).append($groupActivities);
             }
 
             if (more) {
diff --git a/static/scripts/app/views/details.js b/static/scripts/app/views/details.js
index ac83a61826..2cac1118fd 100644
--- a/static/scripts/app/views/details.js
+++ b/static/scripts/app/views/details.js
@@ -24,37 +24,76 @@ define([
         },
 
         getDetails: function () {
-            var repo_id = this.repo_id, cmmt_id = this.cmmt_id,
-                details_title, item_data, item_html,
-                _this = this;
+            var _this = this;
 
             Common.ajaxGet({
-                get_url: Common.getUrl({ name:'get_history_changes', repo_id: repo_id}),
-                data: {'commit_id': cmmt_id},
+                get_url: Common.getUrl({
+                    name:'get_history_changes',
+                    repo_id: this.repo_id
+                }),
+                data: {'commit_id': this.cmmt_id},
                 after_op_success: function (data) {
                     _this.$('.loading-tip').hide();
                     _this.$('.commit-time').html(data['date_time']);
 
-                    for (var item in data) {
-                        if (item == "cmt_desc") {
-                            _this.$el.append(data[item]);
-                        } else if (data[item].length > 0 && item != 'date_time') {
-                            if (item == "new") { details_title = gettext("New files") }
-                            if (item == "removed") { details_title = gettext("Deleted files") }
-                            if (item == "renamed") { details_title = gettext("Renamed or Moved files") }
-                            if (item == "modified") { details_title = gettext("Modified files") }
-                            if (item == "newdir") { details_title = gettext("New directories") }
-                            if (item == "deldir") { details_title = gettext("Deleted directories") }
-
-                            item_data = {"details_title": details_title, "details": data[item]};
-                            item_html = _this.detailItemTemplate(item_data);
-                            _this.$el.append(item_html);
-                        }
+                    var showDetails = function(params) {
+                        _this.$el.append(_this.detailItemTemplate({
+                            "details_title": params.title,
+                            "details": params.content
+                        }));
+                    };
+                    if (data['new'].length > 0) {
+                        showDetails({
+                            'title': gettext("New files"),
+                            'content': data['new']
+                        });
                     }
+                    if (data['removed'].length > 0) {
+                        showDetails({
+                            'title': gettext("Deleted files"),
+                            'content': data['removed']
+                        });
+                    }
+                    if (data['renamed'].length > 0) {
+                        showDetails({
+                            'title': gettext("Renamed or Moved files"),
+                            'content': data['renamed']
+                        });
+                    }
+                    if (data['modified'].length > 0) {
+                        showDetails({
+                            'title': gettext("Modified files"),
+                            'content': data['modified']
+                        });
+                    }
+                    if (data['newdir'].length > 0) {
+                        showDetails({
+                            'title': gettext("New directories"),
+                            'content': data['newdir']
+                        });
+                    }
+                    if (data['deldir'].length > 0) {
+                        showDetails({
+                            'title': gettext("Deleted directories"),
+                            'content': data['deldir']
+                        });
+                    }
+
+                    // most of the time, no 'cmt_desc'
+                    if (data['cmt_desc']) {
+                        _this.$el.append('<p>' + Common.HTMLescape(data['cmt_desc']) + '</p>');
+                    }
+
                     $(window).resize();
                 },
-                after_op_error: function() {
-                    $('#ls-ch').html(gettext("Unknown error"));
+                after_op_error: function(xhr) {
+                    var err_msg;
+                    if (xhr.responseText) {
+                        err_msg = $.parseJSON(xhr.responseText).error;
+                    } else {
+                        err_msg = gettext("Failed. Please check the network.");
+                    }
+                    _this.$el.html('<p class="error">' + err_msg + '</p>');
                     setTimeout(function() { $.modal.close(); }, 2500);
                 }
             });