diff --git a/framework/base/Application.php b/framework/base/Application.php
index 40e8437..cd77f1f 100644
--- a/framework/base/Application.php
+++ b/framework/base/Application.php
@@ -464,7 +464,7 @@ class Application extends Module
 	 */
 	public function renderException($exception)
 	{
-		if ($exception instanceof Exception && ($exception->causedByUser || !YII_DEBUG)) {
+		if ($exception instanceof Exception && ($exception instanceof UserException || !YII_DEBUG)) {
 			$message = $exception->getName() . ': ' . $exception->getMessage();
 		} else {
 			$message = YII_DEBUG ? (string)$exception : 'Error: ' . $exception->getMessage();
diff --git a/framework/base/ErrorHandler.php b/framework/base/ErrorHandler.php
index 0b6bf97..211bad6 100644
--- a/framework/base/ErrorHandler.php
+++ b/framework/base/ErrorHandler.php
@@ -81,7 +81,7 @@ class ErrorHandler extends Component
 				\Yii::$application->renderException($exception);
 			} else {
 				$view = new View($this);
-				if (!YII_DEBUG || $exception instanceof Exception && $exception->causedByUser) {
+				if (!YII_DEBUG || $exception instanceof UserException) {
 					$viewName = $this->errorView;
 				} else {
 					$viewName = $this->exceptionView;
@@ -256,7 +256,7 @@ class ErrorHandler extends Component
 	public function renderAsHtml($exception)
 	{
 		$view = new View($this);
-		if (!YII_DEBUG || $exception instanceof Exception && $exception->causedByUser) {
+		if (!YII_DEBUG || $exception instanceof UserException) {
 			$viewName = $this->errorView;
 		} else {
 			$viewName = $this->exceptionView;
diff --git a/framework/base/Exception.php b/framework/base/Exception.php
index ab681e2..db77028 100644
--- a/framework/base/Exception.php
+++ b/framework/base/Exception.php
@@ -18,11 +18,6 @@ namespace yii\base;
 class Exception extends \Exception
 {
 	/**
-	 * @var boolean whether this exception is caused by end user's mistake (e.g. wrong URL)
-	 */
-	public $causedByUser = false;
-
-	/**
 	 * @return string the user-friendly name of this exception
 	 */
 	public function getName()
diff --git a/framework/base/HttpException.php b/framework/base/HttpException.php
index ca753b9..378b56a 100644
--- a/framework/base/HttpException.php
+++ b/framework/base/HttpException.php
@@ -19,16 +19,12 @@ namespace yii\base;
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @since 2.0
  */
-class HttpException extends Exception
+class HttpException extends UserException
 {
 	/**
 	 * @var integer HTTP status code, such as 403, 404, 500, etc.
 	 */
 	public $statusCode;
-	/**
-	 * @var boolean whether this exception is caused by end user's mistake (e.g. wrong URL)
-	 */
-	public $causedByUser = true;
 
 	/**
 	 * Constructor.
diff --git a/framework/base/InvalidRequestException.php b/framework/base/InvalidRequestException.php
index fd468a1..dddb35e 100644
--- a/framework/base/InvalidRequestException.php
+++ b/framework/base/InvalidRequestException.php
@@ -15,14 +15,9 @@ namespace yii\base;
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @since 2.0
  */
-class InvalidRequestException extends \Exception
+class InvalidRequestException extends UserException
 {
 	/**
-	 * @var boolean whether this exception is caused by end user's mistake (e.g. wrong URL)
-	 */
-	public $causedByUser = true;
-
-	/**
 	 * @return string the user-friendly name of this exception
 	 */
 	public function getName()
diff --git a/framework/base/InvalidRouteException.php b/framework/base/InvalidRouteException.php
index e20b2b7..0d5a9b5 100644
--- a/framework/base/InvalidRouteException.php
+++ b/framework/base/InvalidRouteException.php
@@ -15,14 +15,9 @@ namespace yii\base;
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @since 2.0
  */
-class InvalidRouteException extends \Exception
+class InvalidRouteException extends UserException
 {
 	/**
-	 * @var boolean whether this exception is caused by end user's mistake (e.g. wrong URL)
-	 */
-	public $causedByUser = true;
-
-	/**
 	 * @return string the user-friendly name of this exception
 	 */
 	public function getName()
diff --git a/framework/base/UserException.php b/framework/base/UserException.php
new file mode 100644
index 0000000..f915882
--- /dev/null
+++ b/framework/base/UserException.php
@@ -0,0 +1,21 @@
+<?php
+/**
+ * UserException class file.
+ *
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright &copy; 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\base;
+
+/**
+ * UserException is the base class for exceptions that are meant to be shown to end users.
+ * Such exceptions are often caused by mistakes of end users.
+ *
+ * @author Qiang Xue <qiang.xue@gmail.com>
+ * @since 2.0
+ */
+class UserException extends Exception
+{
+}
diff --git a/framework/console/Application.php b/framework/console/Application.php
index 5f86cac..2f91d5b 100644
--- a/framework/console/Application.php
+++ b/framework/console/Application.php
@@ -126,8 +126,7 @@ class Application extends \yii\base\Application
 			'message' => 'yii\console\controllers\MessageController',
 			'help' => 'yii\console\controllers\HelpController',
 			'migrate' => 'yii\console\controllers\MigrateController',
-			'shell' => 'yii\console\controllers\ShellController',
-			'create' => 'yii\console\controllers\CreateController',
+			'app' => 'yii\console\controllers\CreateController',
 		);
 	}
 
diff --git a/framework/console/Exception.php b/framework/console/Exception.php
index 0ed5a42..63daba3 100644
--- a/framework/console/Exception.php
+++ b/framework/console/Exception.php
@@ -15,14 +15,9 @@ namespace yii\console;
  * @author Qiang Xue <qiang.xue@gmail.com>
  * @since 2.0
  */
-class Exception extends \yii\base\Exception
+class Exception extends \yii\base\UserException
 {
 	/**
-	 * @var boolean whether this exception is caused by end user's mistake (e.g. wrong URL)
-	 */
-	public $causedByUser = true;
-
-	/**
 	 * @return string the user-friendly name of this exception
 	 */
 	public function getName()
diff --git a/framework/console/controllers/HelpController.php b/framework/console/controllers/HelpController.php
index 3e9b4e1..147fde0 100644
--- a/framework/console/controllers/HelpController.php
+++ b/framework/console/controllers/HelpController.php
@@ -52,7 +52,7 @@ class HelpController extends Controller
 	 * @return integer the exit status
 	 * @throws Exception if the command for help is unknown
 	 */
-	public function actionIndex($command)
+	public function actionIndex($command = null)
 	{
 		if ($command !== null) {
 			$result = Yii::$application->createController($command);
@@ -147,10 +147,10 @@ class HelpController extends Controller
 		if ($commands !== array()) {
 			echo "The following commands are available:\n\n";
 			foreach ($commands as $command) {
-				echo " * $command\n";
+				echo "* $command\n";
 			}
 			echo "\nTo see the help of each command, enter:\n";
-			echo "\n    yiic help <command-name>\n\n";
+			echo "\n  yiic help <command-name>\n\n";
 		} else {
 			echo "\nNo commands are found.\n";
 		}