diff --git a/inc/inc.ClassDMS.php b/inc/inc.ClassDMS.php
index 3909d4696..5ee54d11d 100644
--- a/inc/inc.ClassDMS.php
+++ b/inc/inc.ClassDMS.php
@@ -536,7 +536,7 @@ class LetoDMS_DMS {
 
 		$resArr = $resArr[0];
 
-		$user = new LetoDMS_User($resArr["id"], $resArr["login"], $resArr["pwd"], $resArr["fullName"], $resArr["email"], $resArr["language"], $resArr["theme"], $resArr["comment"], $resArr["isAdmin"], $resArr["hidden"]);
+		$user = new LetoDMS_User($resArr["id"], $resArr["login"], $resArr["pwd"], $resArr["fullName"], $resArr["email"], $resArr["language"], $resArr["theme"], $resArr["comment"], $resArr["isAdmin"], $resArr["isGuest"], $resArr["hidden"]);
 		$user->setDMS($this);
 		return $user;
 	} /* }}} */
@@ -558,7 +558,7 @@ class LetoDMS_DMS {
 
 		$resArr = $resArr[0];
 
-		$user = new LetoDMS_User($resArr["id"], $resArr["login"], $resArr["pwd"], $resArr["fullName"], $resArr["email"], $resArr["language"], $resArr["theme"], $resArr["comment"], $resArr["isAdmin"], $resArr["hidden"]);
+		$user = new LetoDMS_User($resArr["id"], $resArr["login"], $resArr["pwd"], $resArr["fullName"], $resArr["email"], $resArr["language"], $resArr["theme"], $resArr["comment"], $resArr["isAdmin"], $resArr["isGuest"], $resArr["hidden"]);
 		$user->setDMS($this);
 		return $user;
 	} /* }}} */
@@ -573,7 +573,7 @@ class LetoDMS_DMS {
 		$users = array();
 
 		for ($i = 0; $i < count($resArr); $i++) {
-			$user = new LetoDMS_User($resArr[$i]["id"], $resArr[$i]["login"], $resArr[$i]["pwd"], $resArr[$i]["fullName"], $resArr[$i]["email"], (isset($resArr["language"])?$resArr["language"]:NULL), (isset($resArr["theme"])?$resArr["theme"]:NULL), $resArr[$i]["comment"], $resArr[$i]["isAdmin"], $resArr[$i]["hidden"]);
+			$user = new LetoDMS_User($resArr[$i]["id"], $resArr[$i]["login"], $resArr[$i]["pwd"], $resArr[$i]["fullName"], $resArr[$i]["email"], (isset($resArr["language"])?$resArr["language"]:NULL), (isset($resArr["theme"])?$resArr["theme"]:NULL), $resArr[$i]["comment"], $resArr[$i]["isAdmin"], $resArr[$i]["isGuest"], $resArr[$i]["hidden"]);
 			$user->setDMS($this);
 			$users[$i] = $user;
 		}
@@ -581,11 +581,11 @@ class LetoDMS_DMS {
 		return $users;
 	} /* }}} */
 
-	function addUser($login, $pwd, $fullName, $email, $language, $theme, $comment, $isAdmin=0, $isHidden=0) { /* {{{ */
+	function addUser($login, $pwd, $fullName, $email, $language, $theme, $comment, $isAdmin=0, $isGuest=0, $isHidden=0) { /* {{{ */
 		if (is_object($this->getUserByLogin($login))) {
 			return false;
 		}
-		$queryStr = "INSERT INTO tblUsers (login, pwd, fullName, email, language, theme, comment, isAdmin, hidden) VALUES ('".$login."', '".$pwd."', '".$fullName."', '".$email."', '".$language."', '".$theme."', '".$comment."', '".$isAdmin."', '".$isHidden."')";
+		$queryStr = "INSERT INTO tblUsers (login, pwd, fullName, email, language, theme, comment, isAdmin, isGuest, hidden) VALUES ('".$login."', '".$pwd."', '".$fullName."', '".$email."', '".$language."', '".$theme."', '".$comment."', '".$isAdmin."', '".$isGuest."', '".$isHidden."')";
 		$res = $this->db->getResult($queryStr);
 		if (!$res)
 			return false;
diff --git a/inc/inc.ClassDocument.php b/inc/inc.ClassDocument.php
index b731d8056..f5ff07102 100644
--- a/inc/inc.ClassDocument.php
+++ b/inc/inc.ClassDocument.php
@@ -510,8 +510,8 @@ class LetoDMS_Document { /* {{{ */
 		/* The owner of the document has unrestricted access */
 		if ($user->getID() == $this->_ownerID) return M_ALL;
 
-		//Gast-Benutzer?? FIXME:
-		if (($user->getID() == $this->_dms->guestID) && ($this->_dms->enableGuestLogin)) {
+		/* The guest users do not have more than read access */
+		if ($user->isGuest()) {
 			$mode = $this->getDefaultAccess();
 			if ($mode >= M_READ) return M_READ;
 			else return M_NONE;
@@ -635,7 +635,7 @@ class LetoDMS_Document { /* {{{ */
 		 * the currently logged in user should be passed to this function
 		 *
 		GLOBAL $user;
-		if ($user->getID() == $this->_dms->guestID) {
+		if ($user->isGuest()) {
 			return -2;
 		}
 		if (!$user->isAdmin()) {
@@ -746,7 +746,7 @@ class LetoDMS_Document { /* {{{ */
 		 * the currently logged in user should be passed to this function
 		 *
 		GLOBAL $user;
-		if ($user->getID() == $this->_dms->guestID) {
+		if ($user->isGuest()) {
 			return -2;
 		}
 		if (!$user->isAdmin()) {
@@ -1252,11 +1252,11 @@ class LetoDMS_Document { /* {{{ */
 					$queryStr = "(SELECT `tblUsers`.* FROM `tblUsers` ".
 						"LEFT JOIN `tblGroupMembers` ON `tblGroupMembers`.`userID`=`tblUsers`.`id` ".
 						"WHERE `tblGroupMembers`.`groupID` IN (". $groupIDs .") ".
-						"AND `tblUsers`.`id` !='".$this->_dms->guestID."')";
+						"AND `tblUsers`.`isGuest` = 0)";
 				}
 				$queryStr .= (strlen($queryStr)==0 ? "" : " UNION ").
 					"(SELECT `tblUsers`.* FROM `tblUsers` ".
-					"WHERE (`tblUsers`.`id` !='".$this->_dms->guestID."') ".
+					"WHERE (`tblUsers`.`isGuest` = 0) ".
 					"AND ((`tblUsers`.`id` = ". $this->_ownerID . ") ".
 					"OR (`tblUsers`.`isAdmin` = 1)".
 					(strlen($userIDs) == 0 ? "" : " OR (`tblUsers`.`id` IN (". $userIDs ."))").
@@ -1267,7 +1267,7 @@ class LetoDMS_Document { /* {{{ */
 					$queryStr = "(SELECT `tblUsers`.* FROM `tblUsers` ".
 						"LEFT JOIN `tblGroupMembers` ON `tblGroupMembers`.`userID`=`tblUsers`.`id` ".
 						"WHERE `tblGroupMembers`.`groupID` NOT IN (". $groupIDs .")".
-						"AND `tblUsers`.`id` != '".$this->_dms->guestID."' ".
+						"AND `tblUsers`.`isGuest` = 0 ".
 						(strlen($userIDs) == 0 ? ")" : " AND (`tblUsers`.`id` NOT IN (". $userIDs .")))");
 				}
 				$queryStr .= (strlen($queryStr)==0 ? "" : " UNION ").
@@ -1276,7 +1276,7 @@ class LetoDMS_Document { /* {{{ */
 					"OR (`tblUsers`.`isAdmin` = 1))".
 					"UNION ".
 					"(SELECT `tblUsers`.* FROM `tblUsers` ".
-					"WHERE `tblUsers`.`id` != '".$this->_dms->guestID."' ".
+					"WHERE `tblUsers`.`isGuest` = 0 ".
 					(strlen($userIDs) == 0 ? ")" : " AND (`tblUsers`.`id` NOT IN (". $userIDs .")))").
 					" ORDER BY `login`";
 			}
diff --git a/inc/inc.ClassFolder.php b/inc/inc.ClassFolder.php
index e4af15f28..727fa4c79 100644
--- a/inc/inc.ClassFolder.php
+++ b/inc/inc.ClassFolder.php
@@ -564,7 +564,7 @@ class LetoDMS_Folder {
 		if ($user->getID() == $this->_ownerID) return M_ALL;
 		
 		/* Guest has read access by default, if guest login is allowed at all */
-		if (($user->getID() == $this->_dms->guestID) && ($this->_dms->enableGuestLogin)) {
+		if ($user->isGuest()) {
 			$mode = $this->getDefaultAccess();
 			if ($mode >= M_READ) return M_READ;
 			else return M_NONE;
@@ -674,11 +674,9 @@ class LetoDMS_Folder {
 		/* Verify that the requesting user has permission to add the target to
 		 * the notification system.
 		 */
-		/*
-		if ($user->getID() == $this->_dms->guestID) {
+		if ($user->isGuest()) {
 			return -2;
 		}
-		*/
 		if (!$user->isAdmin()) {
 			if ($isUser) {
 				if ($user->getID() != $obj->getID()) {
@@ -785,11 +783,9 @@ class LetoDMS_Folder {
 		/* Verify that the requesting user has permission to add the target to
 		 * the notification system.
 		 */
-		/*
-		if ($user->getID() == $this->_dms->guestID) {
+		if ($user->isGuest()) {
 			return -2;
 		}
-		*/
 		if (!$user->isAdmin()) {
 			if ($isUser) {
 				if ($user->getID() != $obj->getID()) {
@@ -848,7 +844,7 @@ class LetoDMS_Folder {
 				$groupIDs .= (strlen($groupIDs)==0 ? "" : ", ") . $group->getGroupID();
 			}
 			foreach ($tmpList["users"] as $user) {
-				if ($user->getUserID()!=$this->_dms->guestID) {
+				if (!$user->isGuest()) {
 					$userIDs .= (strlen($userIDs)==0 ? "" : ", ") . $user->getUserID();
 				}
 			}
@@ -863,11 +859,11 @@ class LetoDMS_Folder {
 					$queryStr = "(SELECT `tblUsers`.* FROM `tblUsers` ".
 						"LEFT JOIN `tblGroupMembers` ON `tblGroupMembers`.`userID`=`tblUsers`.`id` ".
 						"WHERE `tblGroupMembers`.`groupID` IN (". $groupIDs .") ".
-						"AND `tblUsers`.`id` !='".$this->_dms->guestID."')";
+						"AND `tblUsers`.`isGuest` = 0)";
 				}
 				$queryStr .= (strlen($queryStr)==0 ? "" : " UNION ").
 					"(SELECT `tblUsers`.* FROM `tblUsers` ".
-					"WHERE (`tblUsers`.`id` !='".$this->_dms->guestID."') ".
+					"WHERE (`tblUsers`.`isGuest` = 0) ".
 					"AND ((`tblUsers`.`id` = ". $this->_ownerID . ") ".
 					"OR (`tblUsers`.`isAdmin` = 1)".
 					(strlen($userIDs) == 0 ? "" : " OR (`tblUsers`.`id` IN (". $userIDs ."))").
@@ -878,7 +874,7 @@ class LetoDMS_Folder {
 					$queryStr = "(SELECT `tblUsers`.* FROM `tblUsers` ".
 						"LEFT JOIN `tblGroupMembers` ON `tblGroupMembers`.`userID`=`tblUsers`.`id` ".
 						"WHERE `tblGroupMembers`.`groupID` NOT IN (". $groupIDs .")".
-						"AND `tblUsers`.`id` != '".$this->_dms->guestID."' ".
+						"AND `tblUsers`.`isGuest` = 0 ".
 						(strlen($userIDs) == 0 ? ")" : " AND (`tblUsers`.`id` NOT IN (". $userIDs .")))");
 				}
 				$queryStr .= (strlen($queryStr)==0 ? "" : " UNION ").
@@ -887,7 +883,7 @@ class LetoDMS_Folder {
 					"OR (`tblUsers`.`isAdmin` = 1))".
 					"UNION ".
 					"(SELECT `tblUsers`.* FROM `tblUsers` ".
-					"WHERE `tblUsers`.`id` != '".$this->_dms->guestID."' ".
+					"WHERE `tblUsers`.`isGuest` = 0 ".
 					(strlen($userIDs) == 0 ? ")" : " AND (`tblUsers`.`id` NOT IN (". $userIDs .")))").
 					" ORDER BY `login`";
 			}
diff --git a/inc/inc.ClassUI.php b/inc/inc.ClassUI.php
index 0b39a3de2..cf498be02 100644
--- a/inc/inc.ClassUI.php
+++ b/inc/inc.ClassUI.php
@@ -170,8 +170,8 @@ class UI {
 		echo "<ul class=\"globalNav\">\n";
 		echo "<li id=\"first\"><a href=\"../out/out.ViewFolder.php?folderid=".$settings->_rootFolderID."\">".getMLText("content")."</a></li>\n";
 		if ($settings->_enableCalendar) echo "<li><a href=\"../out/out.Calendar.php?mode=".$settings->_calendarDefaultView."\">".getMLText("calendar")."</a></li>\n";
-		if ($user->getID() != $settings->_guestID) echo "<li><a href=\"../out/out.MyDocuments.php?inProcess=1\">".getMLText("my_documents")."</a></li>\n";
-		if ($user->getID() != $settings->_guestID) echo "<li><a href=\"../out/out.MyAccount.php\">".getMLText("my_account")."</a></li>\n";
+		if (!$user->isGuest()) echo "<li><a href=\"../out/out.MyDocuments.php?inProcess=1\">".getMLText("my_documents")."</a></li>\n";
+		if (!$user->isGuest()) echo "<li><a href=\"../out/out.MyAccount.php\">".getMLText("my_account")."</a></li>\n";
 		if ($user->isAdmin()) echo "<li><a href=\"../out/out.AdminTools.php\">".getMLText("admin_tools")."</a></li>\n";
 		echo "<li><a href=\"../out/out.Help.php\">".getMLText("help")."</a></li>\n";
 		echo "<li id=\"search\">\n";
@@ -247,7 +247,7 @@ class UI {
 		$accessMode = $folder->getAccessMode($user);
 		$folderID = $folder->getID();
 		echo "<ul class=\"localNav\">\n";
-		if ($accessMode == M_READ && $user->getID() != $settings->_guestID) {
+		if ($accessMode == M_READ && !$user->isGuest()) {
 			echo "<li id=\"first\"><a href=\"../out/out.FolderNotify.php?folderid=". $folderID ."&showtree=".showtree()."\">".getMLText("edit_folder_notify")."</a></li>\n";
 		}
 		else if ($accessMode >= M_READWRITE) {
@@ -297,7 +297,7 @@ class UI {
 			echo "<li><a href=\"../out/out.RemoveDocument". $docid ."\">".getMLText("rm_document")."</a></li>";
 			echo "<li><a href=\"../out/out.DocumentAccess". $docid ."\">".getMLText("edit_document_access")."</a></li>";
 		}
-		if ($accessMode >= M_READ && $user->getID() != $settings->_guestID) {
+		if ($accessMode >= M_READ && !$user->isGuest()) {
 			echo "<li><a href=\"../out/out.DocumentNotify". $docid ."\">".getMLText("edit_existing_notify")."</a></li>";
 		}
 		echo "</ul>\n";
@@ -360,7 +360,7 @@ class UI {
 		echo "<li><a href=\"../out/out.Calendar.php?mode=w".$ds."\">".getMLText("week_view")."</a></li>\n";
 		echo "<li><a href=\"../out/out.Calendar.php?mode=m".$ds."\">".getMLText("month_view")."</a></li>\n";
 		echo "<li><a href=\"../out/out.Calendar.php?mode=y".$ds."\">".getMLText("year_view")."</a></li>\n";
-		if ($user->getID() != $settings->_guestID) echo "<li><a href=\"../out/out.AddEvent.php\">".getMLText("add_event")."</a></li>\n";
+		if (!$user->isGuest()) echo "<li><a href=\"../out/out.AddEvent.php\">".getMLText("add_event")."</a></li>\n";
 		echo "</ul>\n";
 		return;