diff --git a/classes/Message.php b/classes/Message.php
index 16d0c60b30..fa0c5b3181 100644
--- a/classes/Message.php
+++ b/classes/Message.php
@@ -42,6 +42,7 @@ class Message extends Memcached_DataObject
         $sender = Profile::staticGet('id', $from);
 
         if (!$sender->hasRight(Right::NEWMESSAGE)) {
+            // TRANS: Client exception thrown when a user tries to send a direct message while being banned from sending them.
             throw new ClientException(_('You are banned from sending direct messages.'));
         }
 
@@ -58,6 +59,7 @@ class Message extends Memcached_DataObject
 
         if (!$result) {
             common_log_db_error($msg, 'INSERT', __FILE__);
+            // TRANS: Message given when a message could not be stored on the server.
             return _('Could not insert message.');
         }
 
@@ -68,6 +70,7 @@ class Message extends Memcached_DataObject
 
         if (!$result) {
             common_log_db_error($msg, 'UPDATE', __FILE__);
+            // TRANS: Message given when a message could not be updated on the server.
             return _('Could not update message with new URI.');
         }
 
diff --git a/classes/Profile.php b/classes/Profile.php
index a303469e96..ae6a376021 100644
--- a/classes/Profile.php
+++ b/classes/Profile.php
@@ -735,14 +735,18 @@ class Profile extends Memcached_DataObject
                                             'role' => $name));
 
         if (empty($role)) {
-            throw new Exception('Cannot revoke role "'.$name.'" for user #'.$this->id.'; does not exist.');
+            // TRANS: Exception thrown when trying to revoke an existing role for a user that does not exist.
+            // TRANS: %1$s is the role name, %2$s is the user ID.
+            throw new Exception(sprintf(_('Cannot revoke role "%s" for user #%2$s; does not exist.'),$name, $this->id));
         }
 
         $result = $role->delete();
 
         if (!$result) {
             common_log_db_error($role, 'DELETE', __FILE__);
-            throw new Exception('Cannot revoke role "'.$name.'" for user #'.$this->id.'; database error.');
+            // TRANS: Exception thrown when trying to revoke a role for a user with a failing database query.
+            // TRANS: %1$s is the role name, %2$s is the user ID.
+            throw new Exception(sprintf(_('Cannot revoke role "%1$s" for user #%2$s; database error.'),$name, $this->id));
         }
 
         return true;
diff --git a/classes/Remote_profile.php b/classes/Remote_profile.php
index 0a1676a6a9..77bfbcd99c 100644
--- a/classes/Remote_profile.php
+++ b/classes/Remote_profile.php
@@ -50,7 +50,8 @@ class Remote_profile extends Memcached_DataObject
         if ($profile) {
             return $profile->hasright($right);
         } else {
-            throw new Exception("Missing profile");
+            // TRANS: Exception thrown when a right for a non-existing user profile is checked.
+            throw new Exception(_("Missing profile."));
         }
     }
 }
diff --git a/classes/Status_network.php b/classes/Status_network.php
index a0f3ba5f78..5680c14584 100644
--- a/classes/Status_network.php
+++ b/classes/Status_network.php
@@ -342,6 +342,7 @@ class Status_network extends Safe_DataObject
                 
                 $id = $snt->insert();
                 if (!$id) {
+                    // TRANS: Exception thrown when a tag cannot be saved.
                     throw new Exception(_("Unable to save tag."));
                 }
             }
diff --git a/classes/Subscription.php b/classes/Subscription.php
index 0679c09250..0225ed4df9 100644
--- a/classes/Subscription.php
+++ b/classes/Subscription.php
@@ -71,14 +71,17 @@ class Subscription extends Memcached_DataObject
         }
 
         if (!$subscriber->hasRight(Right::SUBSCRIBE)) {
+            // TRANS: Exception thrown when trying to subscribe while being banned from subscribing.
             throw new Exception(_('You have been banned from subscribing.'));
         }
 
         if (self::exists($subscriber, $other)) {
+            // TRANS: Exception thrown when trying to subscribe while already subscribed.
             throw new Exception(_('Already subscribed!'));
         }
 
         if ($other->hasBlocked($subscriber)) {
+            // TRANS: Exception thrown when trying to subscribe to a user who has blocked the subscribing user.
             throw new Exception(_('User has blocked you.'));
         }
 
@@ -129,6 +132,7 @@ class Subscription extends Memcached_DataObject
 
         if (!$result) {
             common_log_db_error($sub, 'INSERT', __FILE__);
+            // TRANS: Exception thrown when a subscription could not be stored on the server.
             throw new Exception(_('Could not save subscription.'));
         }
 
@@ -160,17 +164,18 @@ class Subscription extends Memcached_DataObject
      * Cancel a subscription
      *
      */
-
     function cancel($subscriber, $other)
     {
         if (!self::exists($subscriber, $other)) {
+            // TRANS: Exception thrown when trying to unsibscribe without a subscription.
             throw new Exception(_('Not subscribed!'));
         }
 
         // Don't allow deleting self subs
 
         if ($subscriber->id == $other->id) {
-            throw new Exception(_('Couldn\'t delete self-subscription.'));
+            // TRANS: Exception thrown when trying to unsubscribe a user from themselves.
+            throw new Exception(_('Could not delete self-subscription.'));
         }
 
         if (Event::handle('StartUnsubscribe', array($subscriber, $other))) {
@@ -197,7 +202,8 @@ class Subscription extends Memcached_DataObject
 
                     if (!$result) {
                         common_log_db_error($token, 'DELETE', __FILE__);
-                        throw new Exception(_('Couldn\'t delete subscription OMB token.'));
+                        // TRANS: Exception thrown when the OMB token for a subscription could not deleted on the server.
+                        throw new Exception(_('Could not delete subscription OMB token.'));
                     }
                 } else {
                     common_log(LOG_ERR, "Couldn't find credentials with token {$token->tok}");
@@ -208,7 +214,8 @@ class Subscription extends Memcached_DataObject
 
             if (!$result) {
                 common_log_db_error($sub, 'DELETE', __FILE__);
-                throw new Exception(_('Couldn\'t delete subscription.'));
+                // TRANS: Exception thrown when a subscription could not be deleted on the server.
+                throw new Exception(_('Could not delete subscription.'));
             }
 
             self::blow('user:notices_with_friends:%d', $subscriber->id);
diff --git a/classes/User.php b/classes/User.php
index cf8d4527b8..8033229c4b 100644
--- a/classes/User.php
+++ b/classes/User.php
@@ -360,11 +360,12 @@ class User extends Memcached_DataObject
                                __FILE__);
                 } else {
                     $notice = Notice::saveNew($welcomeuser->id,
+                                              // TRANS: Notice given on user registration.
+                                              // TRANS: %1$s is the sitename, $2$s is the registering user's nickname.
                                               sprintf(_('Welcome to %1$s, @%2$s!'),
                                                       common_config('site', 'name'),
                                                       $user->nickname),
                                               'system');
-
                 }
             }
 
@@ -375,7 +376,6 @@ class User extends Memcached_DataObject
     }
 
     // Things we do when the email changes
-
     function emailChanged()
     {
 
diff --git a/classes/User_group.php b/classes/User_group.php
index e04c466266..0b83cfd47d 100644
--- a/classes/User_group.php
+++ b/classes/User_group.php
@@ -492,6 +492,7 @@ class User_group extends Memcached_DataObject
 
         if (!$result) {
             common_log_db_error($group, 'INSERT', __FILE__);
+            // TRANS: Server exception thrown when creating a group failed.
             throw new ServerException(_('Could not create group.'));
         }
 
@@ -501,6 +502,7 @@ class User_group extends Memcached_DataObject
             $result = $group->update($orig);
             if (!$result) {
                 common_log_db_error($group, 'UPDATE', __FILE__);
+                // TRANS: Server exception thrown when updating a group URI failed.
                 throw new ServerException(_('Could not set group URI.'));
             }
         }
@@ -508,6 +510,7 @@ class User_group extends Memcached_DataObject
         $result = $group->setAliases($aliases);
 
         if (!$result) {
+            // TRANS: Server exception thrown when creating group aliases failed.
             throw new ServerException(_('Could not create aliases.'));
         }
 
@@ -522,6 +525,7 @@ class User_group extends Memcached_DataObject
 
         if (!$result) {
             common_log_db_error($member, 'INSERT', __FILE__);
+            // TRANS: Server exception thrown when setting group membership failed.
             throw new ServerException(_('Could not set group membership.'));
         }
 
@@ -536,6 +540,7 @@ class User_group extends Memcached_DataObject
 
             if (!$result) {
                 common_log_db_error($local_group, 'INSERT', __FILE__);
+                // TRANS: Server exception thrown when saving local group information failed.
                 throw new ServerException(_('Could not save local group info.'));
             }
         }