Index: t3lib/class.t3lib_flashmessagequeue.php
===================================================================
--- t3lib/class.t3lib_flashmessagequeue.php	(revision 9373)
+++ t3lib/class.t3lib_flashmessagequeue.php	(working copy)
@@ -108,16 +108,40 @@
 	 */
 	public static function renderFlashMessages() {
 		$content = '';
+		$addFadeOutEffectJavascript = FALSE;
 		$flashMessages = self::getAllMessagesAndFlush();
 
 		if (count($flashMessages)) {
 			foreach ($flashMessages as $flashMessage) {
+				if ($flashMessage->getSeverity() <= t3lib_FlashMessage::OK) {
+					$flashMessage->addCssClass('message-fade-out');
+					$addFadeOutEffectJavascript = TRUE;
+				}
+
 				$content .= $flashMessage->render();
 			}
 		}
+
+		if ($addFadeOutEffectJavascript) {
+			self::addFadeOutEffectJavascript();
+		}
+
 		return $content;
 	}
 
+	/**
+	 * Adds the Javascript for the flash messages fade out effect.
+	 *
+	 */
+	protected static function addFadeOutEffectJavascript() {
+		$pageRenderer = t3lib_div::makeInstance('t3lib_PageRenderer');
+
+		$pageRenderer->addExtOnReadyCode('
+			Ext.select(".message-fade-out").each(function(message) {
+				message.pause(5).ghost("t", {remove:true});
+			});
+		');
+	}
 
 }
 
Index: t3lib/class.t3lib_flashmessage.php
===================================================================
--- t3lib/class.t3lib_flashmessage.php	(revision 9373)
+++ t3lib/class.t3lib_flashmessage.php	(working copy)
@@ -43,6 +43,13 @@
 	protected $storeInSession = FALSE;
 
 	/**
+	 * Additional CSS classes to use when rendering the flash message.
+	 *
+	 * @var	array
+	 */
+	protected $additionalCssClasses = array();
+
+	/**
 	 * Constructor for a flash message
 	 *
 	 * @param	string	The message.
@@ -80,6 +87,15 @@
 	}
 
 	/**
+	 * Adds a CSS class when rendering the flash message.
+	 *
+	 * @param	string	The CSS class to add
+	 */
+	public function addCssClass($cssClass) {
+		$this->additionalCssClasses[] = htmlspecialchars($cssClass);
+	}
+
+	/**
 	 * Renders the flash message.
 	 *
 	 * @return	string	The flash message as HTML.
@@ -98,10 +114,14 @@
 			$title = '<div class="message-header">' . $this->title . '</div>';
 		}
 
-		$message = '<div class="typo3-message message-' . $classes[$this->severity] . '">'
+		$message = '<div class="typo3-message '
+			. 'message-' . $classes[$this->severity] . ' '
+			. implode(' ', $this->additionalCssClasses)
+			. '">'
+
 			. $title
 			. '<div class="message-body">' . $this->message . '</div>'
-			. '</div>';
+		. '</div>';
 
 		return $message;
 	}