diff --git a/libreplan-webapp/src/main/java/org/libreplan/web/common/MessagesForUser.java b/libreplan-webapp/src/main/java/org/libreplan/web/common/MessagesForUser.java
index 07e5bf978..1d62686c0 100644
--- a/libreplan-webapp/src/main/java/org/libreplan/web/common/MessagesForUser.java
+++ b/libreplan-webapp/src/main/java/org/libreplan/web/common/MessagesForUser.java
@@ -35,9 +35,13 @@ import org.apache.commons.logging.LogFactory;
import org.hibernate.validator.InvalidValue;
import org.libreplan.business.common.exceptions.ValidationException;
import org.zkoss.zk.ui.Component;
+import org.zkoss.zk.ui.event.CheckEvent;
import org.zkoss.zk.ui.event.Event;
import org.zkoss.zk.ui.event.EventListener;
import org.zkoss.zk.ui.event.Events;
+import org.zkoss.zk.ui.event.InputEvent;
+import org.zkoss.zk.ui.event.MouseEvent;
+import org.zkoss.zk.ui.event.SelectEvent;
import org.zkoss.zk.ui.util.EventInterceptor;
import org.zkoss.zk.ui.util.GenericForwardComposer;
import org.zkoss.zul.Div;
@@ -45,7 +49,12 @@ import org.zkoss.zul.Image;
import org.zkoss.zul.Label;
/**
- * It shows messages to the user.
+ *
+ * It shows messages from the application to the user with different
+ * {@link Level levels} of severity. Once the user does some action in the page,
+ * like clicking a button or changing some input the messages automatically
+ * disappear.
+ *
* @author Óscar González Fernández