diff --git a/front/js/pialert_common.js b/front/js/pialert_common.js
index 4b663b2f..16174bce 100755
--- a/front/js/pialert_common.js
+++ b/front/js/pialert_common.js
@@ -206,7 +206,10 @@ function getString (key) {
 // -----------------------------------------------------------------------------
 // Modal dialog handling
 // -----------------------------------------------------------------------------
-function showModalOk (title, message, callbackFunction = null) {
+function showModalOK (title, message, callbackFunction) {
+  showModalOk (title, message, callbackFunction)
+}
+function showModalOk (title, message, callbackFunction) {
   // set captions
   $('#modal-ok-title').html   (title);
   $('#modal-ok-message').html (message); 
@@ -222,6 +225,8 @@ function showModalOk (title, message, callbackFunction = null) {
   // Show modal
   $('#modal-ok').modal('show');
 }
+
+// -----------------------------------------------------------------------------
 function showModalDefault (title, message, btnCancel, btnOK, callbackFunction) {
   // set captions
   $('#modal-default-title').html   (title);
@@ -253,13 +258,17 @@ function showModalDefaultStrParam (title, message, btnCancel, btnOK, callbackFun
 }
 
 // -----------------------------------------------------------------------------
-function showModalWarning (title, message, btnCancel, btnOK, callbackFunction) {
+function showModalWarning (title, message, btnCancel=getString('Gen_Cancel'), btnOK=getString('Gen_Okay'), callbackFunction=null) {
   // set captions
   $('#modal-warning-title').html   (title);
   $('#modal-warning-message').html (message);
   $('#modal-warning-cancel').html  (btnCancel);
   $('#modal-warning-OK').html      (btnOK);
-  modalCallbackFunction =          callbackFunction;
+
+  if ( callbackFunction != null)
+  {
+    modalCallbackFunction =          callbackFunction;
+  }
 
   // Show modal
   $('#modal-warning').modal('show');
diff --git a/front/network.php b/front/network.php
index 59455c46..e36fcb2c 100755
--- a/front/network.php
+++ b/front/network.php
@@ -456,32 +456,39 @@
 <script>
   $.get('php/server/devices.php?action=getDevicesList&status=all&forceDefaultOrder', function(data) {     
 
-      rawData = JSON.parse (data)      
-
-      devicesListnew = rawData["data"].map(item =>  { return {
-                                                              "name":item[0], 
-                                                              "type":item[2], 
-                                                              "icon":item[3], 
-                                                              "mac":item[11], 
-                                                              "parentMac":item[14], 
-                                                              "rowid":item[13], 
-                                                              "status":item[10],
-                                                              "childrenQty":item[15],
-                                                              "port":item[18]                                                              
-                                                              }})
-
-      setCache('devicesListNew', JSON.stringify(devicesListnew))
-
-      // init global variable
-      deviceListGlobal = devicesListnew;
+    rawData = JSON.parse (data)      
 
+    if(rawData["data"] == "")
+    {
+      showModalOK (getString('Gen_Warning'), getString('Network_NoDevices'))      
       
-      // create tree
-      initTree(getHierarchy());
+      return;
+    }
 
-      // attach on-click events
-      attachTreeEvents();
-    });
+    devicesListnew = rawData["data"].map(item =>  { return {
+                                                            "name":item[0], 
+                                                            "type":item[2], 
+                                                            "icon":item[3], 
+                                                            "mac":item[11], 
+                                                            "parentMac":item[14], 
+                                                            "rowid":item[13], 
+                                                            "status":item[10],
+                                                            "childrenQty":item[15],
+                                                            "port":item[18]                                                              
+                                                            }})
+
+    setCache('devicesListNew', JSON.stringify(devicesListnew))
+
+    // init global variable
+    deviceListGlobal = devicesListnew;
+
+    
+    // create tree
+    initTree(getHierarchy());
+
+    // attach on-click events
+    attachTreeEvents();
+  });
 </script>
 
 
@@ -612,13 +619,25 @@
 
   // --------------------------------------------------------------------------- 
   var myTree;
-  var treeAreaHeight = 800;
+  var visibleTreeArea = $(window).height()-135;
+  var treeAreaHeight = visibleTreeArea > 800 ? 800 : visibleTreeArea;
   var emSize;
   var nodeHeight;
   var sizeCoefficient = 1
 
   function initTree(myHierarchy)
   {
+
+    console.log(myHierarchy)
+    
+
+    if(myHierarchy.type == "")
+    {
+      showModalOk(getString('Network_Configuration_Error'), getString('Network_Root_Not_Configured'))      
+      
+      return;
+    }
+
     // calculate the font size of the leaf nodes to fit everything into the tree area
     leafNodesCount == 0 ? 1 : leafNodesCount;
     emSize = ((treeAreaHeight/(25*leafNodesCount)).toFixed(2));
diff --git a/front/php/templates/language/en_us.json b/front/php/templates/language/en_us.json
index c757b769..021136e8 100755
--- a/front/php/templates/language/en_us.json
+++ b/front/php/templates/language/en_us.json
@@ -22,6 +22,8 @@
             "AppEvents_Helper2" : "Helper 2",
             "AppEvents_Helper3" : "Helper 3",            
             "AppEvents_Extra" : "Extra",            
+            "Gen_Error" : "Error",
+            "Gen_Warning" : "Warning",
             "Gen_Delete" : "Delete",
             "Gen_DeleteAll" : "Delete all",
             "Gen_Cancel" : "Cancel",
@@ -428,6 +430,9 @@
             "Network_Node_Name" : "Node name",
             "Network_Parent" : "Parent network device",
             "Network_Cant_Assign" : "Can't assign the root Internet node as a child leaf node.",
+            "Network_NoDevices" : "Configuration Error",
+            "Network_Configuration_Error" : "Configuration Error",
+            "Network_Root_Not_Configured" : "Select a network device type, for example a <b>Gateway</b>, in the <b>Type</b> field of the <a href=\"deviceDetails.php?mac=Internet\">the Internet root device</a> to start configuring this screen. <br/><br/> More documentation can be found in the <a href=\"https://github.com/jokob-sk/Pi.Alert/blob/main/docs/NETWORK_TREE.md\" target=\"_blank\">How to setup your Network page</a> guide",
             "Network_NoAssignedDevices" : "This network node does not have any assigned devices (leaf nodes). Assign one from bellow or go to the <b><i class=\"fa fa-info-circle\"></i> Details</b> tab of any device in <a href=\"devices.php\"><b> <i class=\"fa fa-laptop\"></i> Devices</b></a>, and assign it to a network <b><i class=\"fa fa-server\"></i> Node (MAC)</b> and <b><i class=\"fa fa-ethernet\"></i> Port</b> there.",
             "Network_Root_Unconfigurable": "Unconfigurable root",
             "HelpFAQ_Title" : "Help / FAQ",