diff --git a/lang/main-de.json b/lang/main-de.json
index 129c45376..3859581f7 100644
--- a/lang/main-de.json
+++ b/lang/main-de.json
@@ -126,6 +126,8 @@
         "mutedTitle": "Stummschaltung aktiv."
     },
     "dialog": {
+        "illCharInRoomNameMessage": "Ungültiges Zeichen im Raumnamen",
+        "roomNameHint": "Ein gültiger Raumname besteht aus Buchstaben, Ziffern, + Zeichen und = Zeichen.",
         "kickMessage": "Oh! Sie wurden aus der Konferenz ausgeschlossen.",
         "popupError": "Ihr Browser blockiert Popup-Fenster von dieser Webseite. Bitte erlauben Sie dieser Seite Popups in den Sicherheitseinstellungen Ihres Browsers und versuchen Sie es erneut.",
         "passwordError": "Diese Konferenz ist mit einem Paswort geschützt. Nur der Besitzer der Konferenz kann ein Passwort vergeben.",
@@ -241,4 +243,4 @@
         "pending": "Die Aufzeichnung wird gestartet sobald ein weiterer Teilnehmer beitritt",
         "on": "Aufzeichnung wurde gestartet"
     }
-}
\ No newline at end of file
+}
diff --git a/lang/main.json b/lang/main.json
index 6b5ff4960..94db5be83 100644
--- a/lang/main.json
+++ b/lang/main.json
@@ -130,7 +130,9 @@
         "mutedTitle": "You're muted!"
     },
     "dialog": {
-        "kickMessage": "Ouch! You have been kicked out of the meet!",
+        "illCharInRoomNameMessage": "Illegal Character in Room Name",
+        "roomNameHint": "A valid room name may contain only letters, digits, + signs and = -characters.",
+        "kickMessage": "Ouch ! You have been kicked out of the meet!",
         "popupError": "Your browser is blocking popup windows from this site. Please enable popups in your browser's security settings and try again.",
         "passwordError": "This conversation is currently protected by a password. Only the owner of the conference can set a password.",
         "passwordError2": "This conversation isn't currently protected by a password. Only the owner of the conference can set a password.",
diff --git a/modules/UI/authentication/LoginDialog.js b/modules/UI/authentication/LoginDialog.js
index 50dff3d3b..9b1673ab8 100644
--- a/modules/UI/authentication/LoginDialog.js
+++ b/modules/UI/authentication/LoginDialog.js
@@ -56,7 +56,8 @@ function Dialog(callback, obtainSession) {
                     var password = f.password;
                     if (jid && password) {
                         stop = false;
-                        //++__authdomain__ complete jid by appending @<domain> if no @ was found in jid
+                        //++__authdomain__ complete jid by appending @<domain> 
+                        //if no @ was found in jid
                         if (jid.indexOf("@") < 0) {
                           jid = jid.concat('@');
                           if (config.hosts.authdomain) {
diff --git a/modules/UI/welcome_page/WelcomePage.js b/modules/UI/welcome_page/WelcomePage.js
index 3a7b9692d..2cd14c04a 100644
--- a/modules/UI/welcome_page/WelcomePage.js
+++ b/modules/UI/welcome_page/WelcomePage.js
@@ -2,14 +2,25 @@
 var animateTimeout, updateTimeout;
 
 var RoomNameGenerator = require("./RoomnameGenerator");
+var messageHandler = require("../util/MessageHandler");
 
 function enter_room() {
     var val = $("#enter_room_field").val();
     if(!val) {
-        val = $("#enter_room_field").attr("room_name");
+      val = $("#enter_room_field").attr("room_name");
     }
     if (val) {
+      // also ÄÖÜäöüß - requiers further changes 
+      // (nginx - sites-enabled (location .. rewrite), other js-modules
+      // var validRoomNamePattern = 
+      // /^[a-zA-Z0-9=\?\+\u00c4\u00e4\u00d6\u00f6\u00dc\u00fc\u00df\ ]+$/;
+      var validRoomNamePattern = /^[a-zA-Z0-9=\?\+]+$/;
+      if (val.match(validRoomNamePattern) !== null) {
         window.location.pathname = "/" + val;
+      } else {
+        messageHandler.openMessageDialog  (
+          "dialog.illCharInRoomNameMessage", "dialog.roomNameHint");
+      }
     }
 }
 
@@ -93,4 +104,4 @@ function setupWelcomePage() {
 
 }
 
-module.exports = setupWelcomePage;
\ No newline at end of file
+module.exports = setupWelcomePage;